Evening primrose oil

Also known as EPO, evening primose oil, gamma linolenic acid.

Last reviewed October 9, 2026 · Jump to references

What is Evening primrose oil?

In plain words

Evening primrose oil is an oil from plant seeds that contains several fats, including gamma-linolenic acid (GLA). The body changes GLA into substances that help regulate inflammation. Researchers study the oil for eczema, breast pain, and menopause symptoms, but studies have not shown consistent benefits.

Technical definition

Evening primrose oil is a seed-derived lipid mixture from Oenothera biennis, composed mainly of triglycerides rich in linoleic acid and containing gamma-linolenic acid (GLA); it is not synonymous with GLA alone. GLA is converted to dihomo-gamma-linolenic acid, a precursor of lipid mediators involved in inflammatory signaling, rather than acting through a single specific receptor. In the United States, evening primrose oil is marketed as a dietary supplement and is not FDA-approved to treat disease.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.