The roots and bark of the shrub Mahonia aquifolium (also called Oregon grape) have traditionally been used both orally and topically to treat skin problems. They were also used for other conditions such as gastritis, fever, hemorrhage, jaundice, gall bladder disease, and cancer. In addition, Mahonia was used as a bitter tonic to improve appetite.

According to some experts, M. aquifolium is identical to the plant named Berberis aquifolium, but others point to small distinctions. Berberis vulgaris, commonly called barberry, is a close relative of these herbs, but is not identical.

Oregon grape is primarily used today as a topical treatment for psoriasis. Growing evidence suggests that it may help reduce symptoms, although it does not seem to be as effective for this purpose as standard medications.1,2,3,15

Oregon grape has been proposed as a treatment for other skin diseases, such as fungal infections (such as athlete's foot), eczema, and acne.4,5,6 However, the evidence is either extremely preliminary or inconclusive. For example, a double-blind, placebo-controlled study of 88 people with eczema tested a cream containing extracts of Mahonia aquifolium, Viola tricolor, and Centella asiatica.17 The results failed to show benefit overall.

Many studies have been performed on purified berberine, a major chemical constituent of Oregon grape and other herbs such as goldenseal, but it is not clear whether their results apply to the whole herb. In addition, impossibly high dosages of the herb would be required to duplicate the amount of berberine used in many of these studies. (For more information, see the article on Goldenseal.)