Evening Primrose Oil

To help treat inflammatory disorders

Evening primrose (Oenothera biennis) adorns many backyards. It grows extensively throughout North America and is now widely naturalized through much of Europe and parts of Asia. Its name comes from its fragrant yellow flowers, measuring about one inch in diameter, which bloom in the evening..

The plant is harvested at the beginning of the flowering season. Oil is extracted from the tiny dark-gray seeds, which are only one fifteenth of an inch (1.5 millimeter) long. The oil is commercially available in capsule form. Each capsule usually contains about 500 milligram of oil. Up to 12 capsules a day, or a half teaspoon of oil, may be used to treat various conditions.

Native Americans are known to have gathered the seeds of evening primrose for food. They also used the plant to treat bruises, wounds, and sore throats. Today’s consumers also use the oil of evening primrose. It is available as a dietary supplement and in soaps and cosmetics. It is claimed that the oil can preserve skin elasticity and prevent wrinkle formation.

Therapeutic Uses of the Oil

Evening primrose oil(EPO) has been used for the treatment of allergy-induced eczema, premenstrual syndrome (PMS), mastalgia (breast pain and tenderness), diabetic neuropathy, and rheumatoid arthritis. Human studies using evening primrose oil have not always met with success. A patient may need to consume evening primrose oil for about three months before a positive clinical response is observed.

A number of human trials found that EPO significantly improved the symptoms of atopic eczema, such as inflammation, itch, skin dryness, and scaliness. In Germany EPO capsules have already been approved for the treatment and symptomatic relief of atopic eczema. The typical dosage is about three to six grams of EPO daily.

Several studies have demonstrated that taking two to three grams of EPO a day may provide significant relief for women with breast pain. Many women report that they experience a marked improvement in PMS symptoms when taking EPO. However, clinical studies have not been consistent in their findings on the benefits of using EPO to treat PMS.

Unique Property of EPO

The health benefits of EPO are attributed to the presence of gamma-linolenic acid (GLA). EPO contains 8 to 14 percent of this unique fatty acid. GLA is a precursor for anti-inflammatory prostaglandins, and may block the formation of similar compounds that are responsible for inflammation. Hence the ratio of noninflammatory to inflammatory compounds is increased with the use of EPO.

The presence of gamma-linolenic acid may explain why many people have used EPO to ameliorate the symptoms of psoriasis, lupus erythematosus, asthma, rheumatoid arthritis, ulcerative colitis, irritable bowel syndrome, and other inflammations. Further scientific studies are needed to validate the usefulness and efficacy of EPO in treating these inflammatory conditions.

There are other plant sources of GLA. These include the oil extracted from black currant seeds (Ribes nigrum) which have 14 to 19 percent GLA, and borage seeds (Borago officinalis), with 20 to 26 percent GLA. Borage seeds do contain small amounts of toxic alkaloids, so borage oil may not be as safe to use as the oil from evening primrose and black currant.

Other Studies

Reports from animal studies have shown the value of using EPO for lowering blood cholesterol levels, diminishing the risk of blood clots, and treating hypertension, but researchers have been unable to verify these effects in human clinical trials.

Cold-pressed EPO was recently found to contain three triterpene derivatives of caffeic acid with a pronounced antioxidant activity and an ability to mop up free radicals. These substances may prevent blood lipids from being oxidized. Only traces of these beneficial substances were found in commercial samples of EPO.

EPO is also considered to be ineffective when used orally by women to shorten labor duration, to prevent pre-eclampsia, and to treat menopausal hot flashes.

Safety Issues

EPO is generally considered to be safe. It has been used in several human studies without any significant side effects. A very small percentage of the population experience some side effects, such as headache, gastrointestinal distress, and nausea. Taking large amounts may also cause loose stools. It is not recommended to use EPO during pregnancy, as it may increase the risk of pregnancy complications. It is, however, safe to use while breast feeding. Since EPO contains a high level of unsaturated fat, it should be stored in a cool place in a dark bottle.

Because EPO possesses antithrombotic properties, it may increase bleeding time. Its use would be contraindicated for those with bleeding disorders. Nosebleeds may result if EPO is used along with herbs such as garlic or ginkgo. In addition, studies suggest that EPO has the potential to lower the seizure threshold in patients with seizure disorders.


The use of EPO has become quite popular for the treatment of PMS symptoms, skin problems, and other inflammatory conditions. It appears to be safe for the majority of people. Further studies are needed to substantiate the many claims made for its use.

Remember: Herbal products and dietary supplements can have pharmacological effects, may produce adverse reactions in some people, and could interact with over-the-counter and prescription medications you may take. Discuss with your physician your decision to use any herbal product. Anything mentioned in this article is not intended to diagnose, prescribe, or treat any ailment.

Winston J. Craig, Ph.D., R.D., is a professor of nutrition at Andrews University, Berrien Springs, Michigan.

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