NEW YORK (Reuters Health) - Taiwanese investigators report that an ointment made from an extract of Indigo naturalis is effective in treatment-resistant plaque psoriasis -- and the treatment appears to be safe.

Indigo naturalis is a plant that is the source of a dark blue dye. The extract has been used for centuries in traditional Chinese medicine for the treatment of psoriasis, the researchers explain in the Archives of Dermatology.

Forty-two patients with recalcitrant plaque psoriasis applied indigo naturalis ointment or vehicle (sham ointment) topically to two symmetrical psoriatic plaque lesions on each side of the body for 12 weeks.

Dr. Yin-Ku Lin of Chang Gung Memorial Hospital in Taoyuan, Taiwan, and colleagues report “significant reductions” in scores of scaling, rash, and induration with indigo naturalis ointment.

The mean sum of these scores was 6.3 with indigo naturalis ointment and 12.8 with the vehicle, and the percentage of the plaque area remaining was 38.5 percent after indigo naturalis treatment compared with 90 percent with the vehicle ointment. Thirty-one of 42 patients (74 percent) experienced clearance or near-clearance of psoriasis lesions with indigo naturalis ointment.

Lin’s group reports that “severity was not a significant factor in predicting treatment success.”

They also point out that “the color and smell of indigo naturalis may affect compliance of the patients and the longer-term durability of the benefit simultaneously. The indigo naturalis ointment slightly stains the skin and clothing, which can be cleaned thoroughly by common detergents. Repeated application has no significant effect on skin color and will not change the skin appearance.”

On the plus side, “Indigo naturalis ointment treatment has neither adverse effects, such as those found with corticosteroid treatment, nor other toxic effects based on our past 5 years of clinical observation. Furthermore, it costs much less in comparison with other topical agents,” Lin and colleagues write. “We anticipate that indigo naturalis ointment can be an alternative or complementary therapy for psoriasis and believe it will be a great benefit to this large patient population.”

SOURCE: Archives of Dermatology, November 2008.

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