Evening Primrose: Benefits, Side-Effects, Supplements, Uses, And Capsules

Evening primrose is any of the flowering plants that belong to the Onagraceae family. Of the over 600 species that belong to this family, it is the common evening primrose, or Oenothera biennis, that is among those of interest to scientists and supplement manufacturers for its health benefits. The common evening primrose, used synonymously with evening primrose in this article unless specified, is a plant with yellow flowers that is endemic to South and North America. The plant, also called the night willow herb, is typically used to treat diseases such as rheumatoid arthritis and atopic dermatitis. It is also used to treat premenstrual syndrome and breast pain. When taken in excess, evening primrose can cause gastrointestinal problems, diarrhea, nausea, and headaches. These side effects are temporary and considered minor. Evening primrose, in general, has a high tolerability profile.

The many components of evening primrose can be processed into different forms for human use. For instance, its seeds are processed into oil (called Evening Primrose Oil or EPO) and powder, which can be further processed into softgels, capsules, or ointments. Its flowers can also be processed into a powder. The leaves of the plant are even utilized in some foods and in teas.

There are many companies that process evening primrose supplements but the top producers are Prescribed Choice, Allergy Research Group, Vital Nutrients, Barlean’s and BodyBio. Most of their products come in gel or capsule form and are consumed orally. The supplements are typically used for hormonal support, skin nourishment, and for the relief of symptoms associated with premenstrual syndrome. 

Evening primrose can also be used to enhance the immune system. The herb, especially the seeds, contains gamma-linolenic acid, an omega-6 fatty acid that is critical to the production of eicosanoids such as prostaglandins. These signaling molecules exhibit anti-inflammatory activity. Excessive and prolonged inflammation has been associated with specific diseases such as cancer, heart disease, and rheumatoid arthritis.

Common evening primrose, known scientifically as Oenothera biennis, belongs to the family Onagraceae. It is also known by other names such as nightlights, evening star, and King’s cure-all. The light references come from the yellow flowers that resemble lights. The reference to the night, meanwhile, is due to the fact that the flowers of this herb bloom open only at night and then stay shut during the day. According to Peter Lesica of the Montana Natural History Center, this may be because the herb has adapted to the pollination practices of moths which fly only at night.

What Are The Benefits Of Evening Primrose?

Evening primrose (common evening primrose) has many reported benefits. Users choose evening primrose for the treatment of many specific diseases and conditions. However, it is important to make a distinction between benefits based on anecdotes versus benefits that have been scientifically proven.

Below we discuss some of the reported benefits of the herb:

1. Helps Clear Up Acne

Evening primrose has been used to clear up acne. However, studies showing the direct positive effects of the herb on acne are limited. A study by Kui Young Park et al was performed using evening primrose oil on xerotic cheilitis, or lip inflammation, in patients with acne undergoing isotretinoin treatment. The study found that the herb did not affect the efficacy of the isotretinoin acne treatment. The researchers noted that the herb reduced patients’ lip inflammation after consumption of the herb st six 450-milligram evening primrose capsules, three times each day for eight weeks.

The belief that the herb can have a positive effect on skin conditions is due in large part to the fact that it contains gamma-linolenic acid. The fatty acid produced from linoleic acid, a critical compound the body needs for development, has been found to suppress inflammatory responses. A study by Cheng Sue Chang et al found that it does this by inhibiting oxidative stress and inactivating nuclear factor KB and activator protein 1, which play a crucial role in inflammation. A meta-analysis of studies on the role of inflammation in acne pathology, conducted by Emil A. Tanghetti, found that the skin condition is an inflammatory disease. The meta-analysis contradicted the popular belief that inflammation takes place only in the late stages of acne lesion development. Rather, the researchers found that there is clinical evidence to show it takes place at all stages.

Based on this evidence, it makes sense for evening primrose to yield positive effects on patients with acne. Supplements in the form of capsules, softgels, and ointment claiming to treat the skin condition continue to proliferate the market. Because there are limited to no studies on the direct effects of evening primrose on acne, it is difficult to give a recommended dosage. Users who wish to treat their skin conditions with the herb should consult a doctor beforehand.

2. Helps Ease Eczema

Scientists are divided on whether evening primrose can help ease eczema, a skin condition that manifests as red and itchy skin. Some scientific studies have shown that the herb does improve this skin condition. A study by Moa Schalin-Karrila et al found a “statistically significant improvement” in eczema patients after they consumed four evening primrose capsules two times daily for 12 weeks. Each capsule contained 360 mg of linoleic acid, 45 mg of gamma-linolenic acid, and 50 mg of oleic acid. The researchers said the improvements were observed in the overall severity of the inflammation. The dosage given reduced the itch and dryness, as well as the surface area affected by eczema. 

Another study by Sabyasachi Banerjee et al found that evening primrose oil improved atopic dermatitis, a common type of eczema, in patients who consumed 500-mg/day for five months. The researchers measured four parameters to determine effects towards the condition: itchiness, the extent of the atopic dermatitis, dryness, and intensity. 

Meanwhile, researchers Bo Young Chung et al concluded that evening primrose oil was a “safe and effective medicine” for the treatment of eczema, particularly for Korean patients with a mild condition. The researchers came to this conclusion after Korean patients aged 2 to 12 given four 450 mg evening primrose oil capsules per day, and a second group of patients aged 13 to 24 given eight 450 mg capsules per day, showed improvements in their Eczema Area Severity Index Scores as compared to the placebo group. The researchers also found there were slight improvements in skin hydration and transepidermal water loss. This is a process by which water evaporates from the skin’s surface eventually leading to unwanted wrinkles.

Some researchers, however, point out that conclusions as to the effectiveness of the herb in treating eczema cannot be made despite the numerous studies. Helen Nankervis et al conducted a systematic review of studies done on possible therapeutic remedies for eczema. They concluded there was “reasonable evidence to suggest no clinically useful benefit” for the use of evening primrose and borage oil, among others. The researchers noted that the studies that used randomized controlled trials and concluded evening primrose was effective in treating eczema merely used small sample sizes and had a poor design. 

Hywel C. Williams conducted a meta-analysis of studies that looked into the use of evening primrose oil for eczema. Williams said there was very little data available in the public domain to make a conclusion as to the herb’s effectiveness. The analysis also noted that many of the trials cited in meta-analyses were unpublished. Williams also noted studies that were done correctly concluded the herb did not yield any benefit to eczema patients. He particularly cited a study by J. Berth-Jones et al, which supplemented patients with 500-mg capsules of evening primrose (each containing 320 mg of linoleic acid and 40 mg of gamma-linolenic acid). Another group was also observed using capsules containing 430 mg of the herb and 107 mg of fish oil, two times a day for 16 weeks. In this study, the herb yielded no therapeutic benefit in patients with atopic dermatitis as compared to the placebo group. 

Because of the different study results, suggesting a dosage to users who wish to treat eczema with evening primrose is difficult. Consultation with a doctor is recommended.

3. Helps Improve Overall Skin Health

Scientific studies have proven evening primrose can improve overall skin health. As previously noted, researcher Bo Young Chung et al concluded that apart from its effects on eczema, the herb improved transepidermal water loss and skin hydration slightly in the patients. A study by R. Muggli observed the overall skin health in terms of skin moisture, transepidermal water loss, fatigue resistance, elasticity, firmness, and roughness in healthy adults. Patients were administered three 500-mg evening primrose oil soft gel capsules for 12 weeks. Muggli observed significant improvement as compared to the placebo group. Muggli attributed evening primrose’s effectiveness to its gamma-linolenic acid content. A study by Asuka Kawamura et al noted that the anti-inflammatory metabolites produced by the fatty acid may be behind the herb’s capacity to improve dry skin. The researchers made this conclusion after noting that the efficacy of gamma-linolenic acid content was greater in patients with inflammatory features. These patients ingested 200 mg of the fatty acid daily. The treatment period, which involved the consumption of creamy wafers containing the gamma-linolenic acid content, was 12 weeks. 

Further research by Rene Van Hoorn et al concluded that gamma-linolenic acid may restore balance in n-6 fatty acids when ingested. Van Hoorn et al noted that those with a “western” lifestyle, in particular, may typically have a surplus of the n-6 fatty acid arachidonic acid, due to diets composed primarily of meats. The n-6 fatty acid gamma-linolenic acid, which is found only in some plants, may be lacking. This imbalance is not favorable to the body. Arachidonic acid produces pro-inflammatory molecules which play a role in the development of skin-related conditions and other diseases. The researchers contended that intake of gamma-linolenic acid enhances the production of anti-inflammatory molecules.

Based on these scientific studies, oral intake of 200 to 500 mg of evening primrose daily for 12 weeks should provide the overall skin-enhancing benefits of the herb. There is no recommended dosage for those considering topical use of the herb since studies on this use are limited. In either case, prior consultation with a doctor is still advised.

4. Helps Relieve PMS Symptoms

Scientific studies have yielded mixed results on the effects of evening primrose on premenstrual syndrome (PMS). A study by Mandana Saki et al, for instance, concluded that the herb was an effective treatment for PMS. The study observed a significant reduction in PMS symptoms in 40 university students following consumption of 1500 mg of the herb daily for three months. Some of these PMS symptoms include fatigue, mood swings, bloating, and headaches. Other researchers, Shinji Watanabe et al, attributed the alleviation of PMS symptoms to the herb’s gamma-linolenic acid content. This conclusion was made after the symptoms–including irritability—significantly improved in women compared to the placebo group. These women consumed vegetable oil, containing 180 mg of gamma-linolenic, per day for three luteal phases. 

On the other hand, SK Khoo et al studied women with moderate PMS following consumption of eight 45-mg evening primrose capsules–four consumed in the morning and the other four at night. Khoo noted while there was an improvement in the symptoms, in the first observed menstrual cycle, this could be due to a strong placebo effect. The researchers observed the severity scores for each of the symptoms–fluid retention, psychological, breast tenderness and menses–as reported by the patients. In their study, symptoms returned after the third of six cycles observed in the study, regardless of whether or not the medication had been given. 

In his meta-analysis of studies on the effects of evening primrose oil on female ailments, D. Budeiri et al concluded evening primrose oil was “of little value” to PMS. They noted the open studies that made conclusions to the contrary were unreliable due to the high placebo rate reported in PMS studies. They said the well-controlled studies, meanwhile, were “small,” meaning if positive effects of evening primrose in PMS were reported, the possibility these were merely “modest” could not be excluded.

Because of the differing study results as to the effects of evening primrose in PMS, it is difficult to suggest a dosage for possible treatment of such. Prior consultation with a doctor is recommended.

5. Helps Minimize Breast Pain

Scientific studies have shown evening primrose helps minimize breast pain, or mastalgia, both cyclical (related to menstrual periods) and non-cyclical. In their study on the effectiveness of three drugs–evening primrose oil, danazol, and bromocriptine–in treating breast pain, J. K. Pye et al concluded evening primrose oil was the “most promising first-line treatment.” This was because of its good tolerability profile. The study showed that of 92 patients treated for cyclical mastalgia, 47 yielded a Grade I or II response. Patients were given six capsules containing the herb consumed daily for three to six months. The researchers said a Grade I response meant an “excellent response” to the treatment with no residual pain. A Grade II response meant a “substantial response” with bearable pain. Of the 33 treated with the herb for non-cyclical mastalgia, nine had a Grade I or II response. J.K. Pye et al found that 95% of the patients who responded to treatment with the herb did so in a period of three months. The same researchers also found, however, that some patients, seven in all, experienced a relapse. The relapsed patients had to be treated with evening primrose oil for another six months even after the initial treatment.

Researchers C.A. Gateley et al made a similar recommendation as to the use of evening primrose oil as “first-line treatment” for breast pain. Three drugs were included in the study, danazol, evening primrose oil, and bromocriptine. The researchers noted, while danazol had the highest response rate in both non-cyclical and cyclical mastalgia, evening primrose oil demonstrated efficacy that was equivalent to that demonstrated by bromocriptine. The primrose oil also had fewer adverse effects reported by patients treated with the herb. According to the researchers, the adverse events reported by patients treated with 3 g daily (with 240 mg of gamma-linolenic acid each) of evening primrose oil for six months were eight-fold less than the events reported by patients treated for danazol and bromocriptine. Of the 241 patients treated with evening primrose oil, three reported abdominal bloating. Nausea, weight gain, headache, depression, giddiness, and rashes were also reported once each as side effects. For danazol, 295 patients were treated with 200 mg daily starting on the second day of the menstrual cycle. Dosage was reduced to 100 mg daily after two months if the response was positive, and then further to dosing only on alternate days or in the last two weeks. Danazol had the following side effect reports: 29 weight gain, 24 menstrual irregularity, 17 headache, 16 nausea and vomiting, eight acne, six abdominal bloating, six hot flashes, four rash, four depression, three reduced breast size, two each hair loss and back pain, one each hirsutism (excess hair) and voice change, and six non-specific items as side-effects. Bromocriptine patients were given 1.25 mg per day. Dosage was increased by 1.25 mg over a period of two weeks until a 2.5-mg dose two times a day was reached. From the 216 patients, researchers received these reports of side effects; 44 nausea and vomiting, 23 headache, 19 postural hypotension, five constipation, three each dyspepsia and vasospasm, two depression, one each rashes and nightmares, and six non-specific items as side-effects.

Neither study looked into what specific element of evening primrose yielded the beneficial effect on mastalgia. However, one study by C.A. Gateley et al study mentioned that each 3-g capsule of the herb contained 240 mg of gamma-linolenic acid. Compare this to a study by D.F. Horrobin, which found that women with breast pain had low levels of gamma-linolenic acid. An article published in the 2002 issue of the Royal Cornwall Hospital Trust Design and Publications suggested it may have to do with the levels of polyunsaturated fatty acids–of which gamma-linolenic acid is a precursor–increasing alongside gamma-linolenic acid levels in the body. Polyunsaturated fatty acids have been found to play a role in mammary gland development.

Based on the C.A. Gateley et al study, consumption of 3g/day of evening primrose oil for six months suffices benefit from the breast pain-relieving effects of the herb. Although evening primrose has been found to have good patient acceptability, consultation with a doctor prior to treatment is still recommended.

6. Helps Reduce Hot Flashes

Scientific studies have proven that evening primrose can help in the management of hot flashes, or those sudden bouts of warmth felt in the neck and face, for menopausal women. A study by Farah Farzaneh et al found that the frequency of hot flashes was lessened, the duration shortened, and the severity reduced. Subjects of the study took two 500 mg capsules of evening primrose daily for six weeks. According to the researchers, the improvement percentages of each symptom were 39%, 19% and 42%, respectively. However, while there was an improvement in all three criteria, only the severity criterion was found to have a significant improvement compared to the placebo group. Subjects in both the evening primrose and placebo groups had improved Hot Flash-Related Daily Interference Scale (HFRDIS) scores. 

A comparative study on the effects of evening primrose and black cohosh on hot flashes conducted by Maryam Mehrpooya et al yielded similar findings. The researchers found that women who had consumed evening primrose oil for eight weeks had less severe hot flashes in the eighth week as compared to the first week of treatment. There were “no significant differences” in the hot flash frequency experienced by the subjects in the eighth week and the first week of treatment. The researchers did not assess for hot flash duration. Nevertheless, the researchers noted that the quality of life of the subjects improved after evening primrose treatment, based on their answers in the Menopause-Specific Quality of Life Questionnaire. 

The studies did not mention the specific ingredient in evening primrose that helps in hot flashes but some have suggested it may have to do with its gamma-linolenic acid content. gamma-linolenic acid helps the body create prostaglandins, which help regulate blood flow. According to Rebekah Lucas et al, a hot flash manifests when the skin and peripheral blood flows are enhanced. 

The dosages described in studies that have shown the positive effects of evening primrose on hot flashes vary. The recommended dose for users who wish to use evening primrose for treatment of the condition may vary as well. Consultation with a doctor is recommended.

7. Helps Reduce High Blood Pressure

The results of scientific studies on the effects of evening primrose on high blood pressure vary, depending on the model used. Researchers Masayoshi Soma et al concluded that evening primrose “consistently lowers” blood pressure in spontaneously hypertensive rats that were fed diets supplemented with 10% evening primrose oil for up to 24 weeks. The researchers also noted that the progression of hypertension in the animals was significantly delayed.

One study on humans, however, yielded different results. Researchers Catherine McCarthy et al observed 37 supplements through a population-based study. In the study, evening primrose saw the biggest mean difference (an increase) in the systolic blood pressure reported by subjects who consumed the herb at least once per week for 12 months and the systolic blood pressure of subjects who did not consume the herb. According to the researchers, the mean systolic blood pressure of non-users was 125.4, compared to the mean systolic blood pressure of evening primrose users 130.1. An increase in the mean diastolic blood pressure was also found, from 73.1 in non-users to 74.3 for evening primrose users. The researchers said that a causal effect between the supplements analyzed in the study and the effects on blood pressure could not be concluded. They did note though, the data proved “intriguing” and could be used for further research.

Scientists who attest to evening primrose’s effectiveness in lowering blood pressure cite the proven positive effects of gamma-linolenic acid on blood pressure as proof. A study by Childebert St. Louis et al found that the fatty acid exerts antihypertensive effects in spontaneously hypertensive rats that received injections of the compound in olive oil. The results were the same across different dosages–1.2 mg/kg/injection, 3.6mg/kg/injection, and 7.2mg/kg/injection two times a day for 12 weeks. The researchers noted that in a week’s time, the animals’ systolic blood pressure decreased from 175+-4 to 145+-4 mm Hg. Their systolic blood pressure, meanwhile, normalized after two weeks. The researchers noted, however, the mechanism by which gamma-linolenic acid regulates blood pressure is unknown.

Because of the conflicting study results, it is difficult to recommend a specific dosage of evening primrose for the treatment of high blood pressure. Users who wish to treat high blood pressure with evening primrose should consult a doctor prior to use.

8. Helps Improve Heart Health

Studies have found evening primrose can improve heart health. A study by Noha M. Abo-Gresha et al found that the electrocardiographic patterns of hypercholesterolemic rats improved after consumption of 5 or 10 grams/kg/day of the herb for six weeks. The researchers also found that platelet aggregation, which is a mark of cardiovascular disease, also improved.  

 

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While there are some studies that do not show the direct effects of evening primrose on the heart, they do prove the positive effects on other critical body systems that have a direct effect on heart health. For instance, a meta-analysis of studies on the effects of evening primrose oil on lipid profile using randomized clinical trials was conducted by Masoud Khorshidi et al. They concluded that consumption of the herb at a dose of up to 4 g/day leads to a significant increase in high-density lipoprotein (HDL) and a decrease in triglycerides. An increase in HDL levels traditionally means an increase in “good cholesterol”. Good cholesterol helps remove bad cholesterol which clogs arteries and leads to cardiovascular disease. A decrease in triglycerides, the most common fat, meanwhile, means a reduced risk of plaque buildup that can lead to heart disease.

The Masayoshi Soma et al study that concluded the antihypertensive effects of evening primrose using an animal model is also noteworthy. A meta-analysis of studies that looked into the relationship between lower blood pressure and cardiovascular disease was performed by Dena Ettehad et al. The meta-analysis noted that every decrease of 10 mm Hg in the systolic blood pressure results in a significant reduction in the risk of heart failure, stroke, coronary heart disease, and other cardiovascular events. It is worth noting that some studies have refuted these claims on the antihypertensive effects of the herb.

The researchers in these studies attributed the positive effects of evening primrose on heart health to its gamma-linolenic acid content. According to Noha M. Abo-Gresha et al, dihomo gamma-linolenic acid is produced by the elongation of gamma-linolenic acid. This new compound helps reduce inflammation in the ischemic heart associated with cardiovascular diseases. Researchers have also observed hypocholesterolemic and antihypertensive effects (although the second one is contested). They note, the specific mechanisms by which these are exercised are not known.

The Masoud Khorshidi et al meta-analysis of studies on the effects of evening primrose on lipid profiles specifically noted that consumption of the herb at a dose of up to 4 g/day yields good cholesterol benefits. However, consultation with a doctor is still advised prior to treatment.

9.  Helps Reduce Nerve Pain

Evening primrose has been found to help improve nerve function. A study by N. E. Cameron et al found that evening primrose improved nerve conduction in diabetic rats. A group of subjects was given the evening primrose for one month after three months without treatment of diabetes. The researchers found that after using evening primrose for only four days following three months of untreated diabetes, the nerve conduction velocity in these rats fell within the normal range. This velocity rapidly decreased over 24 hours when the herb treatment was stopped. Since prolonged use of the herb resulted in the formation of new blood vessels, the researchers concluded evening primrose improves nerve function through a vascular action. Researchers said this was more likely not undertaken by a single component but by the herb’s “complex” composition as a whole.

Another study by Omar Badiri et al also concluded evening primrose improved the nerve functions in rats. The subjects right sciatic nerve had been crushed with a forceps for the experiment. According to the researchers, the rats given a dosage of 450 mg/kg per day of the herb for 28 days recovered the function of their crushed sciatic nerve more quickly than the group that was given only a saline solution. Muscular atrophy or muscle tissue thinning also improved in the rats administered the herb. Omar Badiri et al attributed the positive effects of the herb on nerve function to its gamma-linolenic acid content. This component plays a critical role in ensuring the neural membrane structure, they noted.

The studies that concluded evening primrose yields positive effects on the nerve function used animal models. Human studies would be needed to give a recommended dosage for users who wish to utilize the herb to improve their nerve function. Consultation with a doctor prior to treatment is advised. 

10. Helps Ease Bone Pain

Several studies have shown that evening primrose may help ease bone pain. A study by M. Brzeski et al concluded that the herb may help relieve pain in patients with mild rheumatoid arthritis. This is a disease that sees the immune system attacking healthy cells, resulting in inflammation and pain, particularly in the joints. The researchers came to this conclusion after administering patients with 6g/day of the herb for six months. Patients saw a statistically significant improvement in morning joint stiffness and in the articular index. 

A meta-analysis of studies on the positive effects of several herbs on bone pain was also conducted by Melanie Cameron el al. They concluded there was some evidence to suggest that the gamma-linolenic acid content in evening primrose, blackcurrant seed oil and borage could relieve the pain associated with rheumatoid arthritis. According to M. Brzeski et al, gamma-linolenic acid content is a precursor to dihomo gamma-linolenic acid. This increases the 1-series prostaglandins which, in turn, exhibit anti-inflammatory effects.

The M. Brzeski et al study noted that a dosage of 6g/day of evening primrose for six months can ease bone pain. Nevertheless, consultation with a doctor is advised prior to treatment.

What Are The Risks (Side-Effects) Of Evening Primrose?

Evening primrose has a high tolerability profile. However, when taken in excess, evening primrose can result in the following side-effects:

  • Gastrointestinal problems
  • Diarrhea
  • Nausea
  • Headaches

According to Dr. Bryan Bayles, these side effects are minor and temporary. They typically go away in a short amount of time.

What Is The Nutritional Profile Of Evening Primrose?

Evening primrose has a high nutritional value. It contains Omega-6 essential fatty acids. According to Magdalena Timoszuk et al, evening primrose oil is 73.88% linoleic acid and 9.24% gamma-linolenic acid. The remaining fatty acids in evening primrose oil are oleic acid (6.93%), palmitic acid (6.31%), stearic acid (1.88%), vaccenic acid (0.81%), eicosenoic acid (0.55%), eicosanoic acid (0.31%) and behenic acid (0.10%). 

Evening primrose seed ash also contains 1800 mg of Calcium, 530 mg of Magnesium, 460 mg of Potassium, 18 mg of Sodium, 410 mg of Phosphorus, 39 mg of Iron, 7 mg of Zinc, 1.1 mg of copper, and 0.5 mg of Manganese per 100 g of ash.

How Does Evening Primrose Work Within The Human Body?

Scientists attribute many of evening primrose’s health benefits to its gamma-linolenic acid content. gamma-linolenic acid is an omega-6 fatty acid that is critical to the production of metabolites that exhibit anti-inflammatory activity. Excessive and prolonged inflammation has been associated with diseases such as cancer, heart disease, and rheumatoid arthritis.

Once gamma-linolenic acid enters the body, it is synthesized and then elongated to form dihomo gamma-linolenic acid. This, in turn, produces anti-inflammatory eicosanoids such as 1-series prostaglandins and 3-series leukotrienes.  According to Rakesh Kapoor et al, on its own, gamma-linolenic acid also influences gene expression through the regulation of gene products that play a critical role in the death of potentially virus-infected or damaged cells.

How Do You Determine The Correct Evening Primrose Dosage?

The correct evening primrose dosage will depend on the condition or disease a user seeks to treat. According to Dr. Bryan Bayles, based on scientific studies, the recommended dosage for adults who wish to treat atopic dermatitis ranges from 0.16 to 0.64 g (160 to 640 mg) of gamma-linolenic acid every day for three to 16 weeks. For children with the condition, the recommended dosage, meanwhile, is 0.08 g to 0.32 g (80 to 320 mg) of gamma-linolenic acid every day. Based on scientific studies on the effects of evening primrose on nerve function, the recommended dosage is from 0.36 g to 0.48 g (360 to 480 mg) of gamma-linolenic acid for six months. A one-gram capsule containing the standardized Efamol formula contains 0.062 g of oleic acid, 0.62 g of linoleic acid, and 0.08 g of gamma-linolenic acid. 

Because of the varying recommended dosages and the possible interaction of the herb with other medications, consultation with a doctor prior to treatment with evening primrose is recommended. Researchers have noted that evening primrose has a high tolerability profile. If taken in excess, the side effects one can experience are mild and temporary. 

What Are The Most Common Questions For Evening Primrose Usage?

Many of the questions users ask concerning the use of evening primrose revolve around the possible side effects of the herb, the correct dosage, and the herb’s benefits on health. Here is a list of some of those frequently asked questions, according to Google:

  • What is the best dose of evening primrose oil?
  • Is evening primrose oil safe?
  • What are the side effects of evening primrose?
  • What does evening primrose do for a woman?
  • What is evening primrose oil used to treat?
  • Who should not take evening primrose oil?
  • Does evening primrose oil make you gain weight?
  • Does evening primrose oil increase estrogen?

Users don’t typically ask questions about the ways to consume evening primrose. This may be due to the fact that consumption of the herb is straightforward (orally or topically) and does not require a complex process to be followed.

What Are The Facts About Evening Primrose?

There are many interesting facts about evening primrose. For instance, the herb stands from 2 to 6 feet tall and emits a lemony scent that attracts moths flying at night. This is precisely why one can only see the flowers open at night. The herb, in essence, has adapted to the flying patterns of moths that ensure plant pollination.

Evening primrose is considered an invasive plant species. That means it can spread even in areas that are normally not considered its habitat. The plant is native to North America and typically grows in moist and well-drained soil.

How Is Evening Primrose Processed?

Evening primrose can be processed in different ways. The leaves may be collected and consumed as they are for tea or as food ingredients. The flowers can also be processed into a powder. 

However, evening primrose supplement manufacturers typically focus on the seeds because they are believed to contain much of the gamma-linolenic acid content that yields benefits to humans. According to Song Min Lee et al, the seeds can be prepared in different ways. In their study, they aimed to determine the optimal processing method that maximizes the benefits of evening primrose seeds. Song Min Lee et al said the seeds can be left as they are, roasted, steamed, or transformed into powder. 

For their experiment, the researchers described not subjecting the seeds to any processing method, roasting the seeds on a pan at 302 to 320 degrees Fahrenheit (150 to 160 degrees Celsius), steaming the seeds at 249.8 degrees Fahrenheit (121 degrees Celsius) for 15 minutes, and producing powder from the seeds with a household juicer. Of these methods, the researchers concluded it was the evening primrose transformed into a powder that yielded the most nutritional value (vitamin E, phenolic content, fatty acids). It was also this form that yielded the most antioxidant activity based on antioxidant power assays.

The process of extracting oil from evening primrose seeds is probably the most complex. There are many ways oil can be extracted from the herb. A common way is to use the “cold-pressing” extraction method. Under this process, a hydraulic press is used to crush the seed, forcing natural oils out. Some evening primrose manufacturers have argued that such a method produces subpar evening primrose oils. This is due to their prolonged exposure to air and temperatures reaching as high as 302 degrees Fahrenheit (150 degrees Celsius).

ABC Machinery has described a low-temperature sub-critical solvent extraction. This process derives the oil from evening primrose seeds using special equipment that subjects the same to a pressure range of from 0.3 MPa to 1.0 MPA but at room temperature. According to ABC Machinery, with this method, the original content in the seeds is retained in the resulting extract. This process may yield the most optimal health benefits when consumed because the compounds stay intact and unchanged.

What Are The Supplement Forms Of Evening Primrose?

Evening primrose supplements can come in different forms. Users who wish to avail of evening primrose health benefits may consume the herb in either one of the following forms:  

1. Evening Primrose Liquid Extract

Evening primrose liquid extract is the liquid derived from evening primrose seeds that are either cold-pressed or undergo a low-temperature sub-critical solvent extraction. Also commonly called evening primrose, this liquid extract can be used in different ways. It can be applied topically to the affected area or can be used as a dietary supplement, mixed with water or food.

The recommended dose for evening primrose liquid extract varies, depending on how it is used. 

The recommended dose for each product is specified by the manufacturer. For instance, the recommended dosage for Nature’s Answer liquid evening primrose oil consumed orally is ½ teaspoon or 2.5 ml daily with 6.8 oz of food or water. For NOW brand of EPO, which is applied topically, it is ⅛ of a teaspoon, which is equivalent to one 500-mg softgel.

Why Is Evening Primrose Extract Useful?

Evening Primrose extract is useful and beneficial because, when consumed orally, liquid extracts, in general, allow for faster absorption and optimized use. Since the body doesn’t need to break liquid extracts down for digestion, it goes straight into the bloodstream. According to Medicare Europe, liquid extracts only need one to four minutes to be assimilated into the body. Once assimilated, of the total amount of liquid extract that enters the body, Medicare Europe said 98% is used. 

Liquid extracts applied topically are also a good alternative to oral administration. This particularly applies to patients who find it difficult to swallow medicines in any form. With topical administration of medicine, the risk of medicinal rejection through vomiting is not possible. 

There are also disadvantages to the use of evening primrose liquid extract. Patients have a greater chance of overdosing with the consumption of any medication orally in liquid form. Unlike tablets and pills which have fixed dosages, liquid extracts are more flexible in terms of the dose a patient ends up consuming. The dose consumed by patients will ultimately depend on what they themselves or the health care workers administer.

2. Evening Primrose Pills And Capsules

Evening primrose supplements can also come in solid form. Many of the scientific studies that have proven their benefits have used evening primrose in its softgel form. Many manufacturers provide this form as well. Capsules in the strictest sense have a gelatin or cellulose casing, are opaque and contain powder. Softgels, on the other hand, have a soft casing, are translucent and contain liquid. Evening primrose softgels are essentially liquid extracts that are enclosed in a specialized cover. They are usually consumed with water during meals. 

Like liquid extracts, softgels can be easily digested. Consumers of softgels, though, have more control over dosage, since each softgel sold by the manufacturer already comes with a specific dose. One Prescribed Choice softgel, for instance, contains a fixed dose of 1300 mg of evening primrose oil. Alternatively, one Allergy Research Group softgel contains a fixed dose of 500 mg of the herb in liquid form.

Some scientific studies have also described using these softgels vaginally during women’s labor. A study by Shadab Shahali et al concluded that when used this way, the herb enhances cervical ripening for childbirth. For Shadab Shahali’s study, each softgel contained 1000 mg of evening primrose oil.

Some evening primrose supplements are also sold in vegetarian capsules. Vegcaps are similar to softgels in terms of how they work in the body but are made of vegetable cellulose. Vegcaps are said to be more stable than softgels because of their low moisture content.  

What Are The Evening Primrose Types?

Although evening primrose is typically equated with the yellow-flowered plant that yields health benefits (common evening primrose), there are other plants that belong to the same family. Below are some evening primrose types:

  • Snow Mountain Evening Primrose: This type of evening primrose is native to the mountains of northern California. It grows in rock cracks and in areas where there is typically no soil. It has purple flowers.
  • Alpine Willowherb: This relative is endemic to the Alps. It grows in wet areas, typically where there is snow or a stream. Its flowers are pink.
  • White Flower Willowherb: This evening primrose type can be found in the western and northeastern sections of North America. It grows in cliffs, near streams, and even on the side of roads. Its flowers are white.
  • Fringed Willowherb: Native to North America, East Asia, and the southern part of South America, this type grows in wet areas such as floodplains, marshes, and swamps.

Flowers of the different evening primrose types come in the same form: With four petals and four sepals. A sepal is the part of the flower that encloses the petals. In plants belonging to the evening primrose family, the sepals are also typically folded backward.

What Is The Etymology Of Evening Primrose?

The evening primrose that yields health benefits and is, therefore, of interest to supplement manufacturers is Oenothera biennis. According to Lawrence E. Steckel et al, the genus name Oenothera was coined by Carl Linnaeus, the father of modern taxonomy, in his book Systema Naturae. The word Oenothera is a combination of two Greek words, “oinos”, which means wine, and “thera”, which means “scenting”. The term “biennis”, the researcher said, refers to the biennial plant cycle.

 

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What Place Does Evening Primrose Have In Society And Culture?

Evening primrose plays an important role in society and culture. Even before the herb was transformed into supplement forms to treat diseases such as diabetes, infertility, and osteoporosis, and conditions such as acne and hair loss in the US, it was already used by native indigenous tribes in its raw form to treat conditions such as sore throat and gastrointestinal problems. According to the National Center for Complementary and Integrative Health, native Americans created poultices from evening primrose to treat wounds and bruises. The juices from the leaves and the stems were also applied to the skin to treat skin inflammation. Native indigenous tribes would swallow evening primrose leaves raw to treat sore throats and gastrointestinal conditions. 

At present, evening primrose plays an important role in the nutraceutical and food industry. Supplements are used to treat premenstrual syndrome, eczema, nerve-related conditions, and even baldness and acne. According to Fact.MR’s 2022 Evening Primrose Oil Market Research Report, there is high demand for the herb. In particular, the US and European countries such as France, the United Kingdom and Mexico are the largest markets for evening primrose medicinally. In Asia, the herb is typically used for cosmetic purposes. Of the countries that have a high demand for evening primrose, the US, the report said, is the top importer. China is the top exporter of the herb. The report noted that its total export value of $669.2 million in 2002 increased to $2.4 billion in 2016.

The report forecasts a continued boom in the evening primrose nutraceutical and food industry. Increasing awareness of the proven scientific benefits of the herb and the herb’s low cost has made it a popular health supplement. The price range for evening primrose supplements on the Premier Formulas website is between $10.99 to $64.99, depending on the brand. 

What Are Some Food Recipes That Contain Evening Primrose?

There are many food recipes that include evening primrose as an ingredient. Here is a list of some known recipes:

  • Pickled evening primrose roots: The roots are soaked in apple cider vinegar with rosemary and garlic. The roots are eaten as they are after soaking.
  • Evening primrose roasted seeds: Roast the seeds in the oven for 15 to 20 minutes. The recommended temperature is 350 degrees Fahrenheit. You can eat the seeds alone or sprinkle them on bread and salads.
  • Boiled evening primrose root: Pick the first-year roots to boil in water for 20 to 30 minutes. The boiled roots can be eaten plain, but some consumers prefer butter lathered on them.
  • Evening primrose flower salad: The yellow flowers can be made into salads, mixed with other greens such as lettuce and kale. The flowers are said to have a lemon or citrus flavor.

All parts of the herb are edible and can be made into something in the kitchen.

What Are The Evening Primrose Parts?

Evening primrose has the typical parts of a plant. It has:

  • Flowers: The flowers of Oenothera biennis are yellow. The other plants that belong to the evening primrose family have colors ranging from white to purple. In general, plants belonging to the evening primrose family have four petals.
  • Stem: The plants that belong to the evening primrose family have a central stem covered in white hair that can stand from 2 to 6 feet tall (Oenothera biennis, in particular, only reaches 2 feet tall). Other stems are typically seen branching out from this central stem, giving the herb a bushy look. The stems are green or have a light red color.
  • Seeds: The seeds are small and brown. They can be carried away easily by the wind. They can grow into plants even after staying on the ground for 70 years. 
  • Roots: The roots are brown, fleshy, and long.
  • Leaves: The leaves are green. Smaller leaves can appear on the central stem, in between the big leaves that can be up to eight inches long and two inches wide.

To the inexperienced, it can be difficult to distinguish evening primrose from other plants that have similar physical characteristics. 

What Is The History Of Evening Primrose?

According to Lawrence E. Steckel et al, evening primrose (Oenothera) originated from Central America and may have spread to North America during the ice ages. Europe, the researchers said, began importing Oenothera biennis from North America in 1870 for what was believed to be its health benefits. Because the plant can easily spread and adapt to other environments apart from its habitat, this evening primrose type spread across Eastern and Central Europe in the 1970s. According to Yu Cheng Deng et al, from North America, the herb arrived in northeast China over 100 years ago. It was initially utilized there to feed animals and was eaten by humans during times of famine. The researchers said demand for the seeds, in particular, increased since the 1980s. This was following research studies that found benefits for the use of their gamma-linolenic acid content.  

At present, the researchers said the plant can also be found in Japan, South Africa and Australia. The top exporter, according to Fact.MR’s 2022 Evening Primrose Oil Market Research Report, is China.

What Are The Other Plants That Are Called Evening Primrose From Time To Time?

Some plants have been erroneously called common evening primrose because of their resemblance to the herb. Such plants include:

  • Primrose: The scientific name of this plant is Primula vulgaris. Like evening primrose, it has yellow flowers. Primrose, however, has a limited spread. It should be near the mother plant for it to transform into a full-grown plant.
  • Hairy evening primrose: This plant’s scientific name is Oenothera villosa. It belongs to the same family as common evening primrose. However, the hairs found on the stem of hairy evening primrose are at a uniform distance from each other. The hairs on the stem of common evening primrose are at varied distances from each other.
  • Northern evening primrose: This plant’s scientific name is Oenothera parviflora. It belongs to the same family as common evening primrose. However, the sepal appendages of northern evening primrose are found below the sepal’s tip, while those of common evening primrose are found at the tip.

By and large, an experienced botanist is needed to distinguish evening primrose (Oenothera biennis) from the others.

Are Evening Primrose Supplements Approved By The Authorities?

No. The Food and Drug Administration regulates herbal supplements like evening primrose oil supplements as dietary supplements, not as drugs. That means that these supplements don’t need prior approval from the FDA to be sold on the market. However, once they are on the market, the FDA starts exercising its safety monitoring function. It reviews supplement labels and promotional materials as its resources allow and monitors whether there are safety complaints about the product. The supplement manufacturer itself is required to report any of these complaints to the FDA within 15 days upon receipt of the same.

Can You Take Evening Primrose At Night?

Yes. Evening primrose has a high tolerability profile. If taken in excess, it can cause gastrointestinal problems, diarrhea, nausea, and headaches but these are minor side-effects and typically disappear after a short period of time. 

What is considered excessive dosage depends on the type of condition or disease one wishes to treat with the herb. According to Dr. Bryan Bayles, based on scientific studies, for example, the recommended dosage for adults who wish to treat atopic dermatitis ranges from 0.16 to 0.64 g (160 to 640 mg) of gamma-linolenic acid every day for three to 16 weeks. For children with the condition, the recommended dosage is 0.08 g to 0.32 g (80 to 320 g) of gamma-linolenic acid every day. Based on scientific studies on the effects of evening primrose on nerve function, the researcher said the recommended dosage is from 0.36 g to 0.48 g (360 to 480 g) of gamma-linolenic acid for six months. Anything in excess of those may lead to minor side effects.

Can You Take Evening Primrose After Meal?

Yes, you can. However, if orally consumed, manufacturers recommend consuming the herb regardless of the form during meals. Nature’s Answer, for instance, recommends taking ½ teaspoon of liquid evening primrose oil with 6 to 8 oz of water or food daily. Allergy Research Group recommends taking one to two of its 500-mg evening primrose oil softgels two to three times a day with meals. The recommendations were made perhaps to ensure faster absorption of the herb into the body as the food is digested. It’s best to follow the manufacturer’s recommended time of day the herb should be consumed. Consultation with a medical professional is also advised.

Can You Take Evening Primrose Every Day?

Yes, you can. In fact, that is the recommendation of many evening primrose supplement manufacturers. Prescribed Choice, for instance, recommends taking one of its 1300-mg evening primrose softgels one to three times daily. Nature’s Answer, for its part, recommends taking ½ teaspoon of liquid evening primrose oil with 6 to 8 oz of water or food every day. XBC, which sells evening primrose oil for topical application, doesn’t specify a period within which the liquid extract should be administered but noted that it should be applied “generously” for optimal benefits.

Can A Child Take Evening Primrose?

It is not recommended. According to Dr. Bryan Bayles, the recommended dosage of gamma-linolenic acid for children with atopic dermatitis is 80 to 320 mg every day. Researchers Bo Young Chung et al also concluded that evening primrose oil was a “safe and effective medicine” for the treatment of eczema, particularly for young Korean patients with a mild condition. The researchers came to this conclusion after Korean patients aged 2 to 12 given four 450 mg evening primrose oil capsules per day, and a second group of patients aged 13 to 24 given eight 450 mg capsules per day, showed improvements in their Eczema Area Severity Index Scores as compared to the placebo group. There were slight improvements in skin hydration and transepidermal water loss in the patients after four months of treatment, according to the researchers.

Because of these limited studies that attest to the safety of evening primrose when consumed orally by children, a general conclusion about the herb’s safety when consumed by this group cannot be made. Many of the trials in the studies that found that the herb yielded positive effects on other conditions and diseases such as rheumatoid arthritis, nerve damage, and heart disease involved only adult subjects. Consultation with a medical professional prior to administration of the herb to a child is, therefore, recommended.

Can Your Pet Consume Evening Primrose?

Yes. Some manufacturers even sell evening primrose supplements specifically for dogs and cats. Johnson’s, for instance, notes that consumption of its 500-mg evening primrose oil capsule that contains 10% gamma-linoleic acid promotes healthy skin and coat for the animals. They claim that EPO supplements can also improve their overall health.

The recommended herb dosage depends on the animal and their sizes. According to Johnson’s, cats and small dogs under 10 kilograms should get only one capsule per day while medium dogs weighing 10 to 25 kg should get two to three per day. Large dogs weighing 25 to 45 kg should get three to five capsules per day, Johnson’s said, while very large dogs weighing over 45 kg should get five to six capsules per day.

Which Plant Produces The Evening Primrose?

Evening primrose is the plant. In the broadest sense of the term, evening primrose refers to any of the flowering plants that belong to the Onagraceae family. However, evening primrose is typically equated with common evening primrose or Oenothera biennis, an evening primrose species from which evening primrose oil is derived. It is evening primrose oil (EPO) that is of particular interest to supplement manufacturers due to the health benefits it has been proven to yield.

Evening primrose oil is typically used to treat diseases such as rheumatoid arthritis and atopic dermatitis. It is also used to treat premenstrual syndrome and breast pain.

What Are The Top Scientific Research Topics For Evening Primrose?

Evening primrose is of interest to researchers as well, with many studies revolving around the plant as a therapeutic remedy and its composition. Below are the top scientific topics on evening primrose:

  • Evening primrose oil in the management of menopause symptoms
  • Evening primrose oil in the management of menstrual symptoms
  • Studies on the uses and cultivation of evening primrose
  • Evening primrose (Oenothera biennis) biological activity dependent on chemical composition
  • Studies on the cultivation and uses of evening primrose in China
  • The effect of evening primrose oil on fatigue and quality of life

Researchers also typically look at the ways evening primrose is cultivated and its history.

Can Anyone Take Evening Primrose Supplement?

No. Many of the trials in the studies that have proven the health benefits of evening primrose on humans involved only adults. As such, use of the herb by children is not advisable except if it is used topically or recommended by a physician. According to Dr. Bryan Bayles, the recommended dosage of gamma-linolenic acid for children with atopic dermatitis is 80 to 320 mg each day. Pregnant women are also not advised to take the herb orally. Researchers Dorinda Dove et al, who analyzed the records of pregnant women in the northeastern United States between January 1991 and September 1998 also found that pregnant women who consumed evening primrose oil 500 mg three times every day for one week starting at week 37 of gestation, and then 500 mg once every day until their labor had more labor abnormalities. However, the herb may be administered to pregnant women vaginally. A study by Shadab Shahali et al, for instance, showed that vaginal insertion of a 1000-mg evening primrose capsule in pregnant women led to cervical ripening for labor inducement.

How Long Should You Take Evening Primrose Supplement To See Results?

The recommended treatment period for users of evening primrose supplements varies depending on the type of condition or disease they seek to address. For instance, according to Dr. Bryan Bayles, the treatment period for adults who wish to treat atopic dermatitis ranges from three to 16 weeks, at a dose range of 160 to 640 mg of gamma-linolenic acid every day. Bayles said based on scientific studies on the effects of evening primrose on nerve function, the recommended treatment period is six months, at a dose range of 360 to 480 mg of gamma-linolenic acid, for one to see results. To treat mild rheumatoid arthritis, the study by Brzeski et al concluded that a treatment period of six months at a dose of  6g/day can lead to a statistically significant improvement in morning joint stiffness and in the articular index.

When Is The Best Time To Take Evening Primrose Supplement?

During meals. Many evening primrose manufacturers recommend oral consumption of the herb during this time. For example, Allergy Research Group recommends taking one to two of its 500 mg evening primrose oil softgels two to three times a day with meals. This recommendation is perhaps to ensure rapid absorption of the herb into the body as the food is digested.

What Is The Best Form Of Evening Primrose Supplement For The Skin?

Evening primrose oil softgels are the best evening primrose supplements for the skin. This is because the trials in the many studies that found that the herb yielded positive effects on overall skin health involved oral use of the same by the subjects. A study by R. Muggli found that overall skin health in terms of skin moisture, transepidermal water loss (the process by which water evaporates from the skin’s surface) can lead to unwanted wrinkles, fatigue resistance, elasticity, firmness, and roughness in healthy adults administered three 500-mg Efamol evening primrose oil soft gel capsules for 12 weeks improved significantly as compared to the placebo group. Researchers Bo Young Chung et al concluded that evening primrose oil was a “safe and effective medicine” for the treatment of mild eczema. The researchers noted that Korean patients given 450 mg of evening primrose oil capsules four to eight times per day showed improvements in their Eczema Area Severity Index Scores as compared to the placebo group. The researchers also found there were slight improvements in skin hydration and transepidermal water loss in the patients after four months of treatment.

 

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Some studies have shown that evening primrose applied topically may also yield skin benefits. According to Jutta Auberger et al, there are observed improvements in the skin of a small number of patients with skin reactions to bortezomib treatment when evening primrose oil is applied on the affected area. Researchers Jurgen Blaak et al also concluded in their meta-analysis of studies that looked into the benefits of evening primrose oil, sweet almond, and jojoba in skincare applications that these were, in effect, “effective ingredients” for these preparations. However, they noted that more data was needed on the “absorption, integration, and processing of topically applied natural oils.”

What Are The Benefits Of Evening Primrose For The Skin?

Based on scientific studies, the following are the skin benefits one can derive from consumption of evening primrose:

  • Improved skin moisture
  • Improved transepidermal water loss or the process by which water evaporates from the skin’s surface that can lead to unwanted wrinkles
  • fatigue resistance
  • Elasticity
  • Firmness
  • Improved texture

According to the R. Muggli et al study, for those who have no skin condition, the recommended dosage is three 500-mg Efamol evening primrose oil soft gel capsules for 12 weeks before the statistically significant effects show.

What Are The Benefits Of Evening Primrose For The Hair?

There are limited to no studies that show that evening primrose directly yields positive effects on the hair when consumed. The study by Ibrahim Ozmen et al is perhaps the only study that looked into evening primrose and its effects on the hair, in particular, in patients with alopecia areata or patchy baldness. The evening primrose oil in the study, however, merely formed part of the studied solution that also included thyme oil, rosemary oil, lavender oil, and atlas cedarwood oil further mixed with carrier oils, jojoba and grapeseed oil. In that study, the solution with evening primrose oil led to moderate to dense hair growth in 75% of the patients as compared to the placebo, which consumed the carrier oils that did not include the aromatherapy substances. The reported benefits of evening primrose on hair may have to do with its gamma-linolenic acid content, which has been found to reduce inflammation that can cause hair loss.

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