Herbs & Supplements:
Oregon Grape
Mahonia aquifolium, Berberis aquifolium

Principal Proposed Uses
  • Psoriasis
Other Proposed Uses
  • Fungal Infections, Eczema, Acne

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.

There is considerable inconsistency about the correct name of this plant. According to some experts, M. aquifolium is identical to Berberis aquifolium, but others point to small distinctions. Berberis vulgaris, commonly called barberry, is a close relative of these herbs, but is not identical.

What Is Oregon Grape Used for Today?

Mahonia is primarily used today as a topical treatment for psoriasis. Preliminary evidence suggests that it may help reduce symptoms, although it does not seem to be as effective as standard medications.^1,2,3

Mahonia has been proposed as a treatment for other skin diseases, such as fungal infections, eczema, and acne.^4,5,6 However, the evidence is extremely preliminary, and human trials must be conducted before we will know whether the herb is really effective for any of these conditions.

Many studies have been performed on purified berberine, a major chemical constituent of Mahonia 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 herb would be required to duplicate the amount of berberine used in many of these studies (for more information, see the article on goldenseal).

What Is the Scientific Evidence for Oregon Grape?

A double-blind placebo-controlled study involving 82 people with psoriasis tested the effectiveness of topical application of Mahonia.⁷ Participants used a placebo ointment on one side of their bodies and Mahonia on the other. According to the participants’ assessments, the Mahonia ointment produced significantly better results. However, the physicians did not observe significant differences between the two. One possible design flaw was that 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 Mahonia.⁸ 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 study in which 443 participants with psoriasis used Mahonia topically for 12 weeks found the herb to be helpful for 73.7% of the group.⁹ Without a placebo group, it’s not possible to know whether Mahonia was truly responsible for the improvement seen, but the trial does help to establish the herb's safety and tolerability (see Safety Issues below).

Laboratory research suggests Mahonia 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.^10,11

Dosage

Topical ointments or creams containing 10% Mahonia extract are generally applied 3 times daily to the affected areas.

Safety Issues

Mahonia appears to be safe when used as directed. In the large open study described above, only 5 of the 443 participants reported side effects of burning, redness, and itching.¹²

However, because Mahonia contains berberine, which has been reported to cause uterine contractions and to increase levels of bilirubin, oral consumption of Mahonia should be avoided by pregnant women.^13,14 Safety in young children, nursing women, or people with severe liver or kidney disease has not been established.

Last reviewed March 2002 by Medical Review Board

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