Evening primrose oil (EPO) is the oil extracted from the seeds of the yellow evening primrose wildflower. It is a rich source of linoleic acid and gamma-linoleic acid (GLA), both omega-6 essential fatty acids. GLA is used to make hormone-like substances called prostaglandins, which can help calm inflammation. Many women use evening primrose oil (EPO) to manage symptoms of pre-menstrual syndrome (PMS) and menopause, such as hot flushes. EPO is also used to help ease skin conditions including eczema and acne.