Evening Primrose Oil: Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

What is Evening Primrose Oil?

Evening primrose oil (EPO) is pressed from the seeds of the Oenothera biennis plant and is rich in gamma-linolenic acid (GLA), an omega-6 fatty acid. It became hugely popular as a remedy for eczema, premenstrual syndrome, breast pain and menopausal symptoms. The popularity, however, has long outpaced the evidence — and in some countries its medical licences for eczema were actually withdrawn after reviews concluded it was ineffective.

What Evening Primrose Oil is commonly used for

In supplements, Evening Primrose Oil is promoted for skin conditions such as eczema and within skin & anti-aging formulas, and for premenstrual, breast-pain and menopausal symptoms. It is one of the clearer examples of a popular supplement whose marketing claims are not well matched by controlled trials.

How Evening Primrose Oil works

The idea behind EPO is that its GLA feeds into the body's anti-inflammatory signalling molecules (prostaglandins), which could in theory calm inflammation in skin and ease hormone-related symptoms. Some people with eczema or PMS have been reported to have lower GLA levels. The problem is that this plausible mechanism has not reliably translated into benefits in well-controlled human trials.

What the evidence says

Here's an honest snapshot of what published research suggests about Evening Primrose Oil — including where the evidence is limited.

• A randomised clinical trial found oral evening primrose oil modestly reduced the intensity of menopausal hot flashes compared with placebo over six weeks. (PubMed)
• A separate randomised controlled trial found evening primrose oil did not significantly reduce hot flashes, though it reduced night sweats — illustrating how inconsistent the results are. (PubMed)
• General background on evening primrose oil is summarised by reputable health references; notably, a Cochrane review concluded that oral EPO does not improve eczema. (MedlinePlus)

Typical dosage used in studies

Studies have used a wide range, often 500–3,000 mg per day (providing varying amounts of GLA) for weeks to months. Where effects appear they are small. This is general information from research, not a recommendation.

Side effects and safety

Evening primrose oil is generally well tolerated, with mild stomach upset, headache or loose stools the most common complaints. There is a theoretical concern about lowering the seizure threshold, so people with epilepsy are sometimes advised caution.

Medication interactions and who should avoid Evening Primrose Oil

Sources & further reading

The evidence summary above is drawn from these sources. For general, authoritative background you can also consult:

• PubMed-indexed study (PMID 23625331)
• PubMed-indexed study (PMID 33942584)
• MedlinePlus
• NIH Office of Dietary Supplements
• NIH National Center for Complementary and Integrative Health

Frequently asked questions

Does evening primrose oil help eczema?

High-quality evidence says no. A Cochrane review found oral EPO did not improve eczema, and some countries withdrew its eczema licences after reviewing the evidence.

Does EPO help menopausal hot flashes?

The trials are mixed — one randomised trial found a modest benefit for hot-flash intensity, while another found no benefit for hot flashes but some reduction in night sweats.

Does EPO help PMS or breast pain?

The evidence is weak and inconsistent. Controlled trials generally do not show it beats placebo, even though it remains a popular choice for these symptoms.

What is GLA?

Gamma-linolenic acid, the omega-6 fatty acid in evening primrose oil that is the basis for its anti-inflammatory claims.

Is evening primrose oil safe?

It is generally well tolerated. Caution is advised with blood thinners and anti-seizure medicines, for people with epilepsy, and before surgery.