Evening primrose oil: eczema, breast pain, menopause and what trials show

Evening primrose oil comes from the seeds of Oenothera biennis. Its distinguishing ingredient is gamma-linolenic acid, an omega-6 fatty acid the body can turn into signalling molecules involved in inflammation and skin barrier function. That plausible chemistry is the origin of most health claims. Capsules, bottled oil and skin creams are sold, and the fatty-acid content varies by brand.

Many parents and adults with atopic eczema have been offered evening primrose oil at some point. When researchers have tested it by mouth against a placebo, it has not shown that it relieves eczema symptoms. The NHS treatment advice for eczema rests instead on emollients applied generously and often, topical corticosteroids for flares, and referral to a dermatologist for severe or persistent disease.

A swallowed capsule cannot replace these. Parents should be aware that stopping prescribed creams in favour of capsules may lead to a flare, and an eczema patch that becomes blistered, crusted, weeping or painful may be infected and needs prompt medical review.

Cyclical breast pain was once a main selling point. Trials suggest evening primrose oil is probably no more effective than placebo for it. Evidence for rheumatoid arthritis, premenstrual syndrome and menopausal symptoms is insufficient to say either way.

The NHS, which offers HRT for menopausal symptoms and non-hormonal options such as CBT, says there is very little evidence of how well herbal remedies work for menopause or how safe they are. Breast pain that is persistent, localised to one area, or accompanied by a lump, skin change or nipple discharge should be assessed by a GP rather than managed with supplements.

• A new lump in the breast needs assessment, even if it is painless.

• Pain that lasts or stays in one spot is worth discussing with your GP.

Some midwifery and pregnancy forums mention using evening primrose oil, orally or vaginally, to ripen the cervix. Studies have given inconsistent results on the prostaglandin effects that would underlie this. Nobody should use it to try to bring on labour without the agreement of their midwife or obstetrician, particularly given the lack of clear safety evidence in pregnancy.

Evening primrose oil is probably safe for most adults when taken by mouth. The commonest side effects are digestive: abdominal pain, nausea and diarrhoea. There is less safety information for children. Taking capsules with food may reduce stomach upset.

The NCCIH advises that interactions with medicines are possible, so anyone on regular prescribed medicines should talk to a pharmacist or GP. The NHS gives the same general advice for herbal products and singles out blood thinners, statins, antidepressants, diabetes medicines, blood-pressure tablets and hormonal contraceptives as groups where interactions occur.

There is no conclusive evidence about safety in pregnancy. In breastfeeding, GLA concentration in breast milk rises, but no harmful effects in infants have been documented. The NHS position is that herbal medicines are generally not recommended in pregnancy and breastfeeding, so check with a midwife or pharmacist before starting.

Evening primrose oil products in the UK are normally food supplements. Because they are not licensed medicines, they are not assessed for effectiveness before sale. The MHRA has pointed out that most herbal products on the UK market are unlicensed and that standards vary, and the NHS advises against buying unlicensed herbal medicines online. If a product is sold with a claim to treat a medical condition, that is a warning sign.