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allowed for sale as a prescription drug for treating eczema and breast pain in Britain, but this approval was later withdrawn.1
What is evening primrose oil?
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 is extracted from the seeds of the plant Oenothera biennis
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
On the next page we look at other conditions that are purported to be treatable using evening primrose oil and we also examine how safe evening primrose oil is.