Oenothera species
Scientific Name: Evening Primrose
Other Names: Fever Plant, OEP, Sun Drop
Should I take it?
Evening primrose is actually a weed. Originating in North America, it has spread to Europe and most other mild climate areas of the world, but it is cultivated mainly in Canada and the United States. Evening primrose plants may reach 8 feet tall. They are biennial, which means they take 2 years to reach maturity. During the first year, only a "rosette" or a cluster of large dark green leaves forms close to the ground. In the second spring, stems develop and the plant flowers. Evening primrose gets its name from the bright yellow rose-like flowers it produces. Blooming throughout the summer months, the flowers of evening primrose each last only one night--opening as the sun goes down, remaining open to attract insects that are active during the night, and then wilting in sunlight. Seed pods that are about 2 inches long contain large numbers of small seeds that are harvested and pressed to produce the oil that is used in medicines and cosmetics.
Recently, prescription-only forms of evening primrose oil that were available in the United Kingdom but not in the United States were withdrawn from the market. While they are considered safe to use, their effectiveness is questionable. Non-prescription dietary supplements containing evening primrose oil are still sold in the U.K. even though studies have failed to prove them effective.
Dosage and Administration
Although it may be available as a liquid oil, oral evening primrose oil is most commonly sold in soft gelatin capsules. Different brands of capsules contain varying amounts of the oil and directions for their use also vary. Individuals who decide to use an evening primrose product should follow the instructions on the package that is purchased.
Some general daily dose ranges used in human studies are:
| Condition | Dose |
|---|
| Breast pain | 3,000 mg to 4,000 mg
(3 grams to 4 grams) |
| Eczema | 4,000 mg to 6,000 mg
(4 grams to 6 grams) |
| Premenstrual Syndrome | 2,000 mg to 4,000 mg
(2 grams to 4 grams) |
| Rheumatoid arthritis | 540 mg to 2,800 mg
(about 0.5 gram to 2.8 grams) |
For topical use, evening primrose oil may be applied as often as needed.
Summary
Evening primrose oil supplies significant amounts of essential fatty acids (EFAs)--notably linoleic acid and gamma linolenic acid (GLA), which may block inflammation. Rheumatoid arthritis, asthma, and other inflammatory diseases may be relieved by taking evening primrose oil. Because evening primrose oil contains estrogen-like isoflavones and because deficiencies of EFAs are associated with symptoms of premenstrual syndrome (PMS) and menopause, oral evening primrose oil supplementation may help to relieve these conditions. Evening primrose oil is also applied topically to treat skin conditions such as acne and psoriasis.
Risks
Because evening primrose oil may cause labor to start, it should not be taken by women who are pregnant. Individuals with epilepsy should also avoid evening primrose oil because it may make seizures more likely to occur.
Side Effects
Most side effects from taking evening primrose oil by mouth are mild. They may include headaches, indigestion, and soft stools.
Interactions
Oral evening primrose oil may increase the blood-thinning effects of drug or herbal anticoagulants or antiplatelets. It may increase the risk of seizures when taken with certain prescription drugs for schizophrenia, non-prescription cough and cold products, or herbals. It may also interfere with anti-epileptic drugs.
Last Revised July 18, 2008
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Should I take it? 
