+ -Text Size

Evening Primrose

Other common name(s): Evening primrose oil; the plant is also called cowslip, fever plant, king’s cure-all, night willow-herb, sun drop, scabish

Scientific/medical name(s): Oenothera biennis


Evening primrose is a flowering plant native to North America that now grows throughout much of Europe and parts of Asia. It blooms every other year and its large, fragrant yellow flowers open at dusk and remain open through the night. In Germany, the plant is called night candle for this reason. The oil extracted from the ripe seeds and the fresh plant is used in herbal remedies.

The oil from the seeds and plant contains gamma-linolenic acid (GLA), an omega-6 fatty acid. GLA is thought to play a key role in many body processes. But omega-6 fatty acids are also abundant in nuts and vegetable oils in the form of linoleic acid. The body can convert linoleic acid to GLA and other omega 6 fatty acids as needed. Note that omega-6 fatty acids are different from omega-3 fatty acids (see Gamma Linolenic Acid [GLA] and Omega-3 Fatty Acids). Omega-3 fatty acids can be found fish and fish oils.


Available scientific evidence does not support evening primrose oil as an effective treatment for preventing or treating cancer. Some studies suggest it may help with the symptoms of rheumatoid arthritis, although further research is needed to confirm this. While the essential fatty acids found in evening primrose play a role in health and disease, these fatty acids are also found in other plant oils.

How is it promoted for use?

Evening primrose is promoted as an herbal remedy for a very broad range of conditions, including dermatitis, premenstrual syndrome, menopausal symptoms, eczema, inflammation, hyperactivity in children, high cholesterol, asthmatic cough, upset stomach, psoriasis, rheumatoid arthritis, and diabetic nerve damage. Some proponents also believe the plant has anti-cancer properties. Some claims of evening primrose’s health benefits are based on the fact that its oil contains the omega-6 fatty acid GLA, as noted above.

What does it involve?

The oil can be purchased in capsules, gelcaps, and liquid form. The powdered plant can be purchased and made into a tea. Daily doses of evening primrose oil have ranged from 2 to 16 capsules of 500 milligrams in clinical trials, although in one study up to 36 capsules a day were used. Some people use skin creams that contain evening primrose cream to moisturize or to treat sunburn or eczema.

What is the history behind it?

In folk medicine, evening primrose has been used to treat asthma, gastrointestinal disorders, whooping cough, and symptoms associated with premenstrual syndrome. The scientific name of the plant, Oenothera biennis, comes from the two Greek words oinos ("wine") and thera ("hunt"), because eating the roots was once believed to increase a person's appetite for wine. Folklore also says that evening primrose counters the effects of drinking too much wine. Use of evening primrose as an herbal remedy is relatively recent. Scientific research on its healing properties began in the 1980s.

What is the evidence?

Available scientific evidence does not support claims that evening primrose oil has any effect on cancer. Most research has been conducted in laboratory settings or involved small numbers of patients.

Research into the use of evening primrose oil for other conditions has been mixed. A 2011 review of 7 studies found that there appeared to be some improvement in pain from rheumatoid arthritis in people who took GLA oils. In this review, it didn’t seem to matter whether the oils came from evening primrose, borage, or black currant seeds. More information is needed from well controlled scientific studies to confirm this effect.

Studies that tested evening primrose oil taken by mouth for the skin conditions atopic dermatitis and eczema showed conflicting results. Results of studies of evening primrose oil for treating premenstrual syndrome, menopause symptoms, breast pain, and psoriasis have been either mixed or not favorable. Most research has been conducted in laboratory settings or involved small numbers of patients.

In late 2002, the U.K. withdrew the prescription forms of fatty acid that were made from evening primrose because there was no good evidence that they worked. A recent review concluded that evening primrose did not help with menopausal symptoms. Large-scale clinical trials involving humans are needed to find out the value of evening primrose in treating any illness.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike companies that produce drugs (which must be tested before being sold), the companies that make supplements are not required to prove to the Food and Drug Administration that their supplements are safe or effective, as long as they don't claim the supplements can prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the herb or substance that is on the label, and some may include other substances (contaminants). Actual amounts per dose may vary between brands or even between different batches of the same brand. In 2007, the FDA wrote new rules to improve the quality of manufacturing for dietary supplements and the proper listing of supplement ingredients. But these rules do not address the safety of the ingredients or their effects on health.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

No major health hazards have been identified with taking evening primrose. Headaches, bloating, and indigestion are reported as possible side effects. One article reported that the fatty acid in primrose oil (GLA) might lower seizure thresholds, so it should not be used by people who have seizures. It may also increase the seizure risk in those who are taking medicines for schizophrenia.

There are also reports that GLA might slow the blood's ability to clot. Evening primrose oil can cause problems if taken with herbs or medicines that slow blood clotting (such as blood-thinning medications like warfarin. There might be other potential interactions between oil of evening primrose and other drugs and herbs. Some of these combinations may be dangerous. Always tell your doctor and pharmacist about any herbs you are taking. Women who are pregnant or breast-feeding should not use this herb.

Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer may have serious health consequences.

To learn more

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer


Belch JJ, Ansell D, Madhok R, O’Dowd A, Sturrock RD. Effects of altering dietary essential fatty acids on requirements for non-steroidal anti-inflammatory drugs in patients with rheumatoid arthritis: a double blind placebo controlled study. Ann Rheum Dis. 1988;47:96-104.

Bown D. Encyclopedia of Herbs & Their Uses. New York, NY: DK Publishing Inc; 1995.

Cameron M, Gagnier JJ, Chrubasik S. Herbal therapy for treating rheumatoid arthritis. Cochrane Database Syst Rev. 2011 Feb 16;(2):CD002948.

Cheema D, Coomarasamy A, El-Toukhy T. Non-hormonal therapy of post-menopausal vasomotor symptoms: a structured evidence-based review. Arch Gynecol Obstet. 2007;276:463-469.

Department of Health (UK). Epogam and Efamast (gamolenic acid) withdrawal of marketing authorisations. CMO’s Update: A communication to all doctors from the Chief Medical Officer. 2002;34:2. Accessed at http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/CMOupdate/DH_4003840 on July 15, 2011.

Drug Digest. Evening primrose. Accessed at http://www.drugdigest.org/DD/DVH/HerbsWho/0,3923,4010|Evening%20Primrose,00.html on July 15, 2011. .

Fetrow CW, Avila JR. Professional's Handbook of Complementary & Alternative Medicines. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.

Goyal A, Mansel RE; Efamast Study Group. A randomized multicenter study of gamolenic acid (Efamast) with and without antioxidant vitamins and minerals in the management of mastalgia. Breast J. 2005;11:41-47.

Gruenwald J., Brendler T, Jaenicke C. PDR for Herbal Medicines. 4th ed. Montvale, NJ: Thomson Healthcare Inc. 2007: 311-315.

Linus Pauling Institute Micronutrient Information Center. Essential Fatty Acids. Accessed at http://lpi.oregonstate.edu/infocenter/othernuts/omega3fa/#metabolism on July 18, 2011.

Kleijnen J. Evening primrose oil. BMJ. 1994;309:824-825.

Memorial Sloan-Kettering Cancer Center. Evening primrose oil. Accessed at http://www.mskcc.org/mskcc/html/69216.cfm on July 15, 2011.

Miller LG. Herbal medicinals: selected clinical considerations focusing on known or potential drug-herb interactions. Arch Intern Med. 1998;158:2200-2211.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 07/18/2011
Last Revised: 02/13/2012