Jarrow Formulas Evening Primrose is a cold-pressed, solvent free oil from evening primrose seeds (Oenothera biennis), a source of Gamma-Linolenic Acid (GLA). GLA is an important omega-6 fatty acid supporting the production of prostaglandins (hormone-like compounds), which play an important role in skin and immune health. Evening primrose oil provides nutritional support for mild discomfort associated with Pms.