An evening primrose flower (Oenothera biennis), the plant whose seeds are pressed
Rosa-Maria Rinkl · CC BY-SA 4.0
How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Evening primrose oil
Seed oil rich in gamma-linolenic acid: no better than a placebo for eczema, breast pain or premenstrual syndrome; a small effect on hot flushes.
Benefits
- Hot flushes: less severe than with a placebo when the oil is taken for less than 6 months, according to a meta-analysis; another (6 trials, 450 women) found shorter flushes, with no clear effect on their number.
- Menopause, in everyday life: in a 6-week trial in 56 women, only the severity of flushes decreased more than with a placebo, with less disruption to social life, couple relationships and sexuality.
- Post-menopausal mood: lower symptom scores than with a placebo after 2 and 4 weeks (100 women, 2 g per day).
- Skin of healthy adults: improved hydration, elasticity, firmness and roughness after 12 weeks, except for redness.
- Adolescent PCOS: more regular periods, less insulin and testosterone after 12 weeks at 1 g per day (76 young girls).
- Painful diabetic neuropathy: lower pain scores in 4 weeks, especially at 1 g every 12 hours, in a placebo-controlled trial in 66 patients.
- Multiple sclerosis: less fatigue and pain, better vitality than with a placebo in 52 patients, without slowing down the disease.
Precautions
Anticoagulants: a study cited by the Cochrane Review found more bleeding in people on warfarin (Coumadin) who were taking evening primrose oil. Prolonged use: a reported case suggests, beyond 1 year, a risk of inflammation, thrombosis and immunosuppression. Adverse effects: mild nausea and headaches; in eczema as in breast pain, no more frequent than with a placebo. Limitations: eczema: the Cochrane Review (19 studies on evening primrose oil) concludes that it is not an effective treatment; only the meta-analysis of Efamol oil trials and a trial of 50 patients find a benefit, and in 58 children it performed no better than a placebo. Breast pain: no more effective than a placebo across 13 trials (1,752 female patients), nor in a 6-month trial in 120 women. Premenstrual syndrome: no effect beyond a placebo in 38 women over six cycles, and the two best-conducted trials found nothing. Menopause: a 6-month trial (56 women) found no benefit on hot flushes, and the 2024 meta-analysis judges the evidence insufficient. Weight and cholesterol: no weight loss in 12 weeks in 100 obese women, no overall effect on cholesterol or triglycerides across six trials. Arthritis and other inflammations: mixed results for rheumatoid arthritis, and evidence too heterogeneous for a strong recommendation.
Recommended dosage
1 to 4 g/day of oil in trials, in 500 mg or 1 g capsules, over 4 weeks to 6 months.
How to take it
- For whom: almost all trials involve women (menopause, painful breasts, PCOS, premenstrual syndrome) or patients (eczema, diabetes, multiple sclerosis).
- Menopause: 1 g per day (two 500 mg capsules) for 6 weeks, or 2 g per day for 4 weeks, in trials that find an effect.
- Triglycerides: only a dose of 4 g per day or less reduced them, and only in a subgroup analysis.
- Duration: the effect on eczema, when it exists, appears between 4 and 8 weeks in the meta-analysis of Efamol oil trials.
- What does not work: eczema (independent meta-analysis), breast pain, premenstrual syndrome, hand eczema and weight.
Did you know?
On eczema, the meta-analysis of Efamol oil trials finds a benefit; the Cochrane Review, across 19 studies, concludes conversely that evening primrose oil is not an effective treatment.
What the studies say
This meta-analysis of six randomized controlled clinical trials investigated the efficacy of evening primrose oil (EPO) for managing menopausal symptoms in 450 women. It revealed a non-statistically significant decrease in the number of hot flashes per day, but a significant reduction in their duration in the EPO group. The intensity of hot flashes also decreased, but without reaching statistical significance. The study suggests further rigorous research to better understand its efficacy.
Larki M, Mohammadi S, Makvandi S. — Journal of caring sciences (2025) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more