Reviews of the available scientific evidence have found no reason to recommend evening primrose oil to help the symptoms of premenstrual syndrome or breast pain.
There is some good research showing that evening primrose oil may be helpful in eczema or atopic dermatitis. And some studies suggest that supplements that contain gamma-linolenic acid (GLA), including evening primrose oil, may be of some benefit to people with rheumatoid arthritis. But more research is needed on the use of evening primrose oil for both of these conditions.