Evening primrose is a plant native to North America, but it grows in Europe and parts of the Southern Hemisphere as well. It has yellow flowers that bloom in the evening. Evening primrose oil contains gamma-linolenic acid (GLA), an essential fatty acid. Essential fatty acids are required by the body for growth and development, and must be obtained from the diet.

• Evening primrose oil has been used since the 1930s for eczema (a condition in which the skin becomes inflamed, itchy, or scaly because of allergies or other irritation).
• More recently it has been used for other conditions involving inflammation, such as rheumatoid arthritis.
• Evening primrose oil is used for conditions affecting women's health, such as breast pain associated with the menstrual cycle, menopausal symptoms, and premenstrual syndrome.
• Other conditions for which evening primrose oil is used include cancer and diabetes.

Evening primrose oil is extracted from the seeds of the evening primrose. The oil is usually put into capsules for use.

What the Science Says

• Evening primrose oil may have modest benefits for eczema, and it may be useful for rheumatoid arthritis and breast pain. However, study results are mixed, and most studies have been small and not well designed.
• Evening primrose oil does not appear to affect menopausal symptoms.
• Although some clinical trials have shown a benefit of evening primrose oil for premenstrual syndrome, the best-designed trials found no effect. There is not enough evidence to support the use of evening primrose oil for other health conditions.

Side Effects and Cautions

• Evening primrose oil is well tolerated by most people. Mild side effects include gastrointestinal upset and headache.
• Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health. This will help ensure coordinated and safe care.