What Is Evening Primrose Oil? | Facts, Uses & Evidence

Evening primrose oil comes from the seeds of a yellow-flowered wildflower native to North America. The oil is pressed from those seeds and sold as a dietary supplement, most often in softgel capsules. Its reputation rests on one unusual ingredient: gamma-linolenic acid (GLA), an omega-6 fatty acid the body can convert into anti-inflammatory compounds. That sounds promising on paper, so it is worth looking at what the evidence actually shows before you spend money on a bottle.

If you’re comparing brands, our tested roundup of the best evening primrose oil options breaks down what to look for in a supplement.

What Is In Evening Primrose Oil, Exactly?

The oil is about 70–74% linoleic acid (LA) and 8–10% gamma-linolenic acid (GLA), with the rest made up of smaller amounts of other fatty acids. Both are omega-6 fatty acids. LA is common in many plant oils, but GLA is the reason this particular oil gets attention — it is relatively rare in food sources and has documented anti-inflammatory properties in laboratory research.

The plant itself, Oenothera biennis, grows wild across the United States. The oil is extracted from the mature seeds, not the flowers or leaves.

What Do People Take Evening Primrose Oil For?

The supplement is marketed for a wide range of conditions, and the list is long: eczema and atopic dermatitis, rheumatoid arthritis, PMS and menstrual cramps, breast pain, menopausal hot flashes, and even diabetic nerve pain. Some women also try it for cervical ripening or labor induction at the end of pregnancy.

• Eczema / atopic dermatitis — the most common use, and the focus of most research.
• Rheumatoid arthritis — often taken alongside conventional medication.
• PMS and breast pain — the second most common use, especially for cyclical breast tenderness.
• Menopause symptoms — mainly hot flashes.
• Pregnancy-related uses — sometimes tried at term, but this is explicitly cautioned against.

What Does The Research Actually Show?

The honest answer is that the evidence is weak. The National Center for Complementary and Integrative Health (NCCIH), the federal agency that studies these products, states plainly that there is not enough evidence to support evening primrose oil for any health condition.

Mayo Clinic’s review of the research reaches the same conclusion, finding that most studies show “little to no help” for atopic dermatitis, breast pain, diabetic neuropathy, and PMS. A 2023 review in PubMed concluded that oral evening primrose oil does not provide clinically significant improvement for atopic dermatitis and is likely ineffective for cyclical breast pain and PMS.

The one area where results are mixed rather than negative is a 2024 systematic review that found some positive signals for diabetes, eczema, hot flashes, and breast pain — but its authors concluded the studies were too varied and low-quality to support any strong recommendation. A lipid meta-analysis found no overall effect on cholesterol or triglycerides, though a subgroup analysis hinted at possible benefit at very specific doses.

For labor induction specifically, the caveat is serious. NCCIH notes that oral and vaginal use has been tried to start labor, but a PubMed review says pregnancy use is not supported and should be avoided. This is not a gray area — it is a clear caution.

What About Skin Application?

However, that is a single study, and NCCIH still states oral EPO has not been shown to help atopic dermatitis. Evidence for applying the oil directly to skin is even more limited.

Is Evening Primrose Oil Safe?

For short-term use, yes. Mayo Clinic lists evening primrose oil as likely safe for most people to take for a short time. The bigger question is whether it does anything useful, and the evidence is simply not there yet.

If you are considering it for a chronic condition like eczema or arthritis, treat it as a supplement to your doctor’s plan, not a replacement. Arthritis UK notes that while many people with rheumatoid arthritis try it, the oil does not appear to change long-term disease activity.

One common mix-up worth noting: evening primrose oil is related to borage oil and black currant seed oil — all three contain GLA — but they are not the same product and should not be treated as interchangeable.

In the United States, evening primrose oil is classified as a dietary supplement, not a drug. That means the FDA does not evaluate it for safety or effectiveness the way it does prescription medications, and manufacturers cannot legally claim it treats or cures any disease.

If you decide to try it despite the mixed evidence, choosing a reputable brand matters. The NCCIH’s evening primrose oil fact sheet has the full government rundown on current research.