Evening primrose oil.

People worldwide use evening primrose oil for skin disorders like eczema and dermatitis. This remedy may benefit men and women alike. Anecdotal evidence says that it may stop hair loss and balance male hormones. Health experts, though, state that there isn't enough proof to support these claims.

Evening Primrose Oil Uses

Also known as "king's cure-all" or "night willow herb," evening primrose is a wildflower with medicinal properties. It comes from the plant Oenothera biennis and boasts high levels of fatty acids, such as gamma-linolenic acid (GLA). Most health stores sell dietary supplements containing evening primrose oil (EPO), which is extracted from the plant's seeds.

According to the Memorial Sloan Kettering Cancer Center, this natural remedy is widely used in the treatment of menopause symptoms, diabetic nerve pain, rheumatoid arthritis, inflammatory skin diseases and more. It's also the go-to choice for many women struggling with premenstrual syndrome (PMS). Its potential benefits are subject to debate, though.

For example, some studies have found that evening primrose oil may help treat eczema and relieve hot flashes in menopausal women. Others show that it's no better than a placebo.

Its effectiveness in the treatment of cancer, inflammatory bowel diseases and PMS requires further investigation. Current evidence suggests that evening primrose may provide relief for rheumatoid arthritis pain and inflammation, breast pain, fatigue and other health complaints, but the results are mixed.

Potential Health Benefits and Caveats

Evening primrose oil is available under several brand names. Its composition — and hence its efficacy — varies from one manufacturer to another.

A review published in the August 2018 edition of the journal Antioxidants assessed the biological activity of EPO. Its beneficial effects were attributed to the high levels of polyphenols, vitamins, minerals, sterols and fatty acids. These bioactive compounds occur naturally in its seeds.

Linoleic acid, for instance, makes up 70 to 74 percent of its content. This polyunsaturated fat may help prevent coronary heart disease, according to an August 2014 review featured in the journal Circulation.

Scientists have found that replacing saturated fat with linoleic acid in the diet may lower the risk of heart disease by 9 percent and the risk of cardiovascular mortality by a staggering 13 percent. Safflower oil, corn oil, soybean oil, sunflower seeds and Brazil nuts are all rich in this nutrient.

Note, though, that linoleic acid isn't entirely safe. Despite its cholesterol-lowering action, this compound can have detrimental effects on health, as reported in a May 2017 review in the journal Healthcare. According to some studies, linoleic acid may trigger inflammation and promote tumor growth. To stay safe, use EPO in moderation and watch your intake of linoleic acid.

The Antioxidants review reports that evening primrose oil is also a good source of oleic acid, myristic acid and stearic acid. Furthermore, it's rich in tryptophan, valine, leucine, lysine and other amino acids that make up protein. As the researchers note, this natural product may help protect against chronic inflammation. Its effectiveness, though, depends on its chemical composition.

The European Medicines Agency (EMA) points out that EPO may relieve itching in dry skin conditions. It might also benefit people with dermatitis, an inflammatory skin disease, but the research is limited. A research paper published in Cochrane in April 2013 doesn't support its use in eczema treatment, suggesting that it produces the same results as placebo.

EPO and Male Pattern Baldness

According to the EMA, evening primrose can be used by teenagers and adults over 12 years old. Proponents say that it's a natural aphrodisiac for both men and women, but there is no evidence to support these claims. Animal studies suggest that EPO may stop hair loss and accelerate hair growth, protecting against alopecia. Unfortunately, it's unclear how the results apply to humans.

Alopecia, often referred to as male pattern baldness, affects nearly 7 million Americans, as reported by the National Alopecia Areata Foundation. It's estimated that about 85 percent of men will develop this autoimmune skin disease and lose their hair before reaching their 50s. The risk is higher among those with parents or siblings suffering from alopecia.

Evening primrose oil is marketed as a natural remedy for hair loss, the primary symptom of alopecia. Manufacturers claim that it may also reduce scalp inflammation and protect the hair from environmental damage due to its high fatty acid content. Again, most studies have been conducted on animals.

Take linoleic acid, for example. This fatty acid is converted to arachidonic acid (AA) in the body, according to the Antioxidants review. A January 2016 study published in the Annals of Dermatology states that arachidonic acid stimulates hair growth due to its action on several growth factors in the hair follicle cells. After analyzing its effects on both humans and animals, researchers concluded that AA may elongate human hair shafts and accelerate hair growth in mice.

Read more: The 12 Best Foods for Healthy Hair

Another study, featured in the journal Phytomedicine in September 2012, confirms the anti-inflammatory action of the sterols in evening primrose oil. Therefore, this natural remedy may help relieve scalp inflammation — a contributing factor to hair loss.

Does EPO Relieve Arthritis Pain?

Evening primrose oil has also been studied as a potential treatment for arthritis. Contrary to popular belief, this isn't "one" disease, but an umbrella term for several disorders affecting the joints. Osteoarthritis (OA), rheumatoid arthritis (RA), psoriatic arthritis and gout are just a few to mention.

Read more: Multiple Sclerosis Vs. Rheumatoid Arthritis

More than 18 percent of American men suffer from arthritis, according to the Centers for Disease Control and Prevention. The risk of developing this condition increases with age. The Arthritis Foundation recommends taking 540 milligrams to 2.8 grams of EPO per day for rheumatoid arthritis.

This natural product may help relieve inflammation and other symptoms of RA, says the Memorial Sloan Kettering Cancer Center. But a research paper published in the European Journal of Pharmacology in August 2016 questions these statements. Although several older studies showed that gamma-linoleic acid, a fatty acid in EPO and other oils, may help reduce morning stiffness, swelling and joint pain in RA, the results may not be accurate.

The National Center for Complementary and Integrative Health states that there's insufficient evidence to support the use of EPO for any disease. Furthermore, its long-term safety hasn't been established.

Make sure you consult your doctor before using this supplement, especially if you take anticoagulant drugs. According to the NCCIH, evening primrose oil has mild side effects and may interact with blood thinners, so it's better to stay on the safe side.