Evening primrose and borage oils, usually taken in capsule form, are marketed to treat everything from cancer and arthritis to menopausal hot flashes and diabetes, though there’s no good clinical research to back up the claims. They’re especially promoted for skin conditions, notably eczema. Both oils are rich in gamma-linolenic acid, which has many effects in the body, such as controlling inflammation.
Recently a review by the independent Cochrane Collaboration evaluated 27 studies testing these oils for the treatment of eczema in 1,600 adults and children for up to 24 weeks. It concluded that the oils work no better than a placebo and that further studies “would be hard to justify.”
The review also cited some research suggesting that evening primrose oil has an anti-clotting effect and may increase the risk of bleeding.