Evening primrose oil has found a number of popular uses and is widely available in supplement form without a prescription.
As a medicine, evening primrose oil has had a chequered history. For example, it was once allowed for sale as a prescription drug for treating eczema and breast pain in Britain, but this approval was later withdrawn.1
Contents of this article:
What is evening primrose oil?
Evening primrose oil is extracted from the seeds of the plant Oenothera biennis
Evening primrose oil is the oil derived from the seeds of the evening primrose (Oenothera biennis) plant.
Often abbreviated to EPO, evening primrose oil is a rich source of omega-6 essential fatty acids.2 In particular, it contains one known as gamma linolenic acid (GLA), which is also found in other plant-based oils.3,4
Evening primrose oil contains linoleic acid as well as GLA - both are essential components of myelin, the protective coating around nerve fibers, and the neuronal cell membrane.2
Commercial preparations of evening primrose oil are typically standardized to 8% GLA and 72% linoleic acid.2
The recommended dose of evening primrose oil is 8 to 12 capsules a day, at a dose of 500 mg each capsule.2
Evening primrose oil for eczema
Treatment with oral evening primrose oil was found in research to give partial correction of an essential fatty acid abnormality associated with eczema (which is also known as atopic dermatitis).4
There is mixed placebo-controlled evidence for evening primrose oil efficacy against eczema, but a meta-analysis of nine trials showed the best effects were against the symptom of itching, although the findings were sponsored by a manufacturer of evening primrose oil supplements.4
Another review has suggested a limited role for supplementation in some patients with eczema - those who do not use high-potency steroids. Evening primrose oil's effect was reduced in people who used steroids, although again the author of the analysis was working for a commercial producer.5,6
Eczema may be effectively treated with conventional medicines but complementary alternatives such as evening primrose oil and borage oil are tried by people who have inadequate improvement or fear side-effects.7
A well-respected review of the evidence conducted by the Cochrane Collaboration concludes that evening primrose oil is no more effective than placebo at treating eczema, and can produce mild, temporary, mainly gastrointestinal side-effects.7
Another review of the evidence has found mixed results, with the positive results being modest for both oral and topical forms of evening primrose oil treatments.8
Evening primrose oil for menopause and premenstrual syndrome
There is limited research on evening primrose oil for menopausal hot flashes.
Hot flashes experienced by women going through the menopause have a number of non-hormonal treatment options but evening primrose oil does not offer evidence of effect1 - the one clinical trial before 2006 found no difference compared with placebo.9,10
A more recent trial published in 2013 included only 56 menopausal women for six weeks of treatment with either evening primrose oil or placebo. The active treatment improved severity of hot flashes in this relatively small study.11
There is no current evidence to support a role for evening primrose oil in easing premenstrual syndrome (PMS)1 - a systematic review of four small, low-powered trials found that doses of EPO ranging from 3 to 6 g daily were not effective in improving overall symptoms of PMS.9
Evening primrose oil for nerve pain
Although some sources say there is insufficient evidence,9 beneficial results have been shown in clinical trials, and taking evening primrose oil for 6 to 12 months may improve the symptoms of nerve damage caused by diabetes.1
In one small randomized trial, for example, there was a statistically significant improvement in neuropathy scores, including nerve conduction tests, for people taking evening primrose oil capsules for 6 months compared with placebo.12
Evening primrose oil for osteoporosis
More research is needed to determine the role evening primrose oil itself might play independently of the other supplements.13
Evening primrose oil for other conditions
Herbal remedies tend to be associated with numerous health claims because the regulation of these products is less rigorous than for prescription drugs, although the UK has recently established a register. To be eligible for inclusion on this list, scientific evidence must be provided relating to the safety, quality and traditional use of the herbal product.14
A long list of conditions are purported to be treated with evening primrose oil but there is limited evidence. The US National Institutes of Health cites evidence from the Natural Medicines Comprehensive Database for a list of conditions for which supplementation with the oil is "possibly ineffective."1
Based on research to suggest evening primrose oil may not be effective, the following are on the list: asthma, ADHD, hepatitis B, high cholesterol, liver cancer, breast pain, obesity, psoriasis, psoriatic arthritis.
A second long list cites "insufficient evidence" to support evening primrose oil treatment: chronic fatigue syndrome, diaper rash, dry eyes, dyslexia, dyspraxia (coordination and movement problems), ichthyosis (scaly, flaky skin), infant development, pregnancy complications, rheumatoid arthritis, schizophrenia, Sjogren's syndrome (an autoimmune disorder affecting tears and saliva), ulcerative colitis, cancer, acne, multiple sclerosis, heart disease, Alzheimer's disease.1
Scleroderma and Raynaud's phenomenon
Scleroderma is an autoimmune disease of the connective tissue characterized by thickening and hardening of various tissues, including the skin and other organs.15
Raynaud's phenomenon/disease - which can cause the fingers to go numb and cold - can be associated with scleroderma and evening primrose oil has been investigated as a treatment in a number of research studies.15
However, all the studies have been small, so further research is needed before the oil could become a recommended treatment.15
Regulatory decision in Britain
In Britain, evening primrose oil used to be approved for treating eczema, under the brand name Epogam, and breast pain (mastalgia, under the brand Efamast).
However, the drug regulator at the time - the British equivalent of the US Food and Drug Administration (the Medicines Control Agency, now called the Medicines and Healthcare products Regulatory Agency) - withdrew the licenses for evening primrose oil products marketed as prescription drugs.1,16
The agency concluded there was not enough evidence in 2002 of effectiveness of evening primrose for these uses.1,16
How safe is evening primrose oil?
Bleeding: there is an anticoagulant (blood-thinning) effect with evening primrose oil so there is a higher risk of bleeding for people taking the blood thinner warfarin (Coumadin).7 Therefore, the oil should not be used by these patients.1 Other drugs that thin the blood may also be a problem taken alongside the oil, including clopidogrel (Plavix) and aspirin.3
Seizures: people with epilepsy or other seizure disorder should avoid taking evening primrose oil as it may increase the chances of having a seizure. Also, people with schizophrenia treated with certain drugs may be at risk of seizure, so medical advice should be sought.1
Anesthesia: evening primrose oil should not be taken within two weeks of going for a general anesthetic because of an increased bleeding risk.1
Written by Markus MacGill