Up to 2% of Americans suffer from psoriasis, a skin condition that leads to an intensely itchy rash with clearly defined borders and scales that resemble silvery mica. The fingernails are also frequently involved, showing pitting or thickening.

Medical treatment for psoriasis includes applications of topical steroids and peeling agents that expose the underlying skin for the steroid to contact. Ultraviolet light can also be used, sometimes combined with coal tar applications or medications called psoralens. Synthetic relatives of vitamin A and vitamin D are also used.

Oregon Grape

Evidence from two double-blind, placebo-controlled trials and one comparative trial suggest that cream made from the herb Oregon grape ( Mahonia) may help reduce symptoms of psoriasis, although it does not seem to be as effective as standard medications.

In a double-blind study published in 2006, 200 people were given either a cream containing 10% Oregon grape extract or placebo twice a day for 3 months.27 The results indicate that the people using Oregon grape experienced greater benefits than those in the placebo group, and the difference was statistically significant. The treatment was well tolerated; although, it caused rash or burning sensation in a few people.

Benefits were also seen in a double-blind, placebo-controlled study of 82 people with psoriasis.11 However, the study design had a significant flaw: the treatment salve was darker in color than the placebo, possibly allowing participants to guess which was which.

Another study found that dithranol, a conventional drug used to treat psoriasis symptoms, was more effective than Oregon grape.12 Regrettably, the authors fail to state whether this study was double-blind. Forty-nine participants applied one treatment to their left side and the other to their right for 4 weeks. Skin biopsies were then analyzed and compared with samples taken at the beginning of the study. The physicians evaluating changes in skin tissue were unaware which treatments had been used on the samples. Greater improvements were seen in the dithranol group.

A large open studyin which 443 participants with psoriasis used Oregon grape topically for 12 weeks found the herb to be helpful for 73.7% of the group.13 Without a placebo group, it's not possible to know whether Oregon grape was truly responsible for the improvement seen, but the trial does help to establish the herb's safety and tolerability.

Laboratory research suggests Oregon grape has some effects at the cellular level that might be helpful in psoriasis, such as slowing the rate of abnormal cell growth and reducing inflammation.14,15

For more information, including dosage and safety issues, see the full Oregon grape article.