Evening primrose oil (EPO) is a natural supplement that contains gamma-linolenic acid (GLA), an omega-6 fatty acid with anti-inflammatory properties. It is used for various conditions, primarily related to women’s health and skin care. It may help alleviate premenstrual syndrome (PMS) symptoms such as bloating, mood swings, headaches, and breast pain (mastalgia). Some studies suggest EPO can help reduce the severity and frequency of hot flashes and night sweats, though research results are inconsistent.