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Evening Primrose Oil

Evening primrose oil is one of the best-studied supplements that mostly does not work. A Cochrane review of 27 trials found no benefit for eczema, and the evidence for PMS, breast pain and menopause symptoms is weak or negative.

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What the science says

  • Does not improve eczema Strong evidence

    A 2013 Cochrane review pooling 27 randomized trials (including 19 of evening primrose oil, n=1,596) concluded that oral evening primrose oil is no more effective than placebo for eczema symptoms, and that further trials of this indication would be hard to justify. This is a rare case of high-quality negative evidence, and it is why regulators in the UK withdrew licences for eczema products.

  • Little effect on menopausal hot flashes Limited evidence

    A randomized trial in 56 women taking 500 mg twice daily for six weeks reported a reduction in hot flash intensity but no significant change in frequency or duration versus placebo. The trial was small, short, and has not been convincingly replicated, so this counts as a weak signal at best.

  • PMS and cyclical breast pain Limited evidence

    Trials in premenstrual syndrome and cyclical mastalgia have been small and largely null once placebo response is accounted for. The mechanistic rationale — supplying gamma-linolenic acid (GLA) to correct a supposed enzyme deficiency — has not been validated in humans.

Dosage & safety

Studied doseTrials have used 500-3,000 mg/day of oil, providing roughly 40-300 mg GLA, for 6-24 weeks. There is no established effective dose, because there is no reliably established effect.
SafetyGenerally well tolerated; nausea, headache, soft stools and abdominal discomfort are the usual side effects. Case reports link it to lowered seizure threshold, so avoid it in epilepsy and with phenothiazines. Mild antiplatelet effect — use caution with warfarin, DOACs, and antiplatelet drugs, and stop two weeks before surgery. Not recommended in pregnancy; some obstetric use to ripen the cervix has been associated with prolonged rupture of membranes and is not supported.

How to take it

TimingTiming does not matter; split larger doses across the day.
With food?With meals, which reduces the nausea and soft stools.
Worth knowingStop it two weeks before any planned surgery, and do not use it in late pregnancy to ripen the cervix — that use is unsupported and associated with prolonged rupture of membranes.

Interactions

With medications

  • phenothiazines (chlorpromazine, fluphenazine) and antiepileptic drugs

    Case reports link evening primrose oil to a lowered seizure threshold, which works against seizure control. avoid if you have epilepsy or take phenothiazines

  • warfarin, DOACs and antiplatelet drugs

    Mild antiplatelet effect adding to anticoagulation. tell your prescriber and stop it two weeks before surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does evening primrose oil help eczema?

No: a 2013 Cochrane review of 27 trials, including 19 of evening primrose oil, concluded it is no more effective than placebo for eczema. This strong negative evidence is why UK regulators withdrew licences for eczema products.

Does evening primrose oil help with menopause hot flashes?

Evidence is limited: one small six-week trial in 56 women taking 500 mg twice daily found reduced hot flash intensity but no change in frequency or duration. This has not been convincingly replicated, so evening primrose oil is a weak option at best.

Does evening primrose oil work for PMS or breast pain?

Trials of evening primrose oil for premenstrual syndrome and cyclical breast pain have been small and largely null once the placebo response is accounted for. The evidence is limited and the GLA-deficiency rationale has not been validated in humans.

Who should avoid evening primrose oil?

Avoid evening primrose oil if you have epilepsy or take phenothiazines, since case reports link it to a lowered seizure threshold. It has a mild antiplatelet effect, so stop it two weeks before surgery, and it is not recommended in pregnancy.

Scientific references

Where to buy

Solgar, Evening Primrose Oil, 1,300 mg, 60 Softgels

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