Evening primrose oil is extracted from the seeds of evening primrose (Oenothera biennis), a plant native to North America. It gets its name from its yellow blossoms, which bloom in the evening.

The oil contains gamma-linolenic acid (GLA) and other omega-6 fatty acids that have both anti-inflammatory and pain-relieving, or analgesic, properties. GLA is used to make hormone-like substances called prostaglandins, which can help calm inflammation

It is thought to help relieve the symptoms of rheumatoid arthritis, eczema, dry or inflamed skin and other inflammatory conditions.