The blue plant-derived powder works to decrease inflammation.

The blue plant-derived powder works to decrease inflammation.(LIBPROJECT.HKBU.EDU/HK)In November, researchers in Taiwan reported that indigo ointment was a safe and effective treatment for psoriasis, a chronic disease that produces inflamed, painful, and itchy lesions on the skin. There are some things you should know about indigo naturalis and the limitations of the latest research.

In a 12-week study, 42 patients applied the ointment, made with a dark blue powder, which is used in Chinese medicine and derived from the Strobilanthes formosanus Moore plant, to a psoriasis plaque on one side of their body. They applied a mixture of petroleum jelly, wax, and olive oil to a corresponding plaque on the other side of their body. At the end of the study, the areas treated with indigo showed an 81% improvement and none of the patients reported serious side effects.

Those results, published in the November 2008 issue of Archives of Dermatology, are promising, but not unexpected, says Heather Zwickey, PhD, dean of research at the National College of Natural Medicine in Portland, Ore.

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"It's pretty well known that indigo is a COX-2 inhibitor, which means it should decrease inflammation," says Zwickey. "The big advantage to this study is that [the treatment] was topical." The oral use of indigo has been associated with gastrointestinal irritation and liver side effects. A topical ointment may be a safer option, but the Taiwanese study isnt conclusive on this point, says Zwickey.

"As far as a treatment of psoriasis symptoms, this is really promising," Zwickey says. But the results are very preliminary. Because the indigo ointment is dark blue, and petroleum jelly is not, patients were aware of which plaques received the indigo, a limitation of the study, the researchers note.

Zwickey says pesticides and other factors affecting the plant itself can also skew study results. The Taiwanese doctors suggest that future research should aim to develop a more potent and absorbable ointment.

"A long-term safety study definitely needs to be done," says Zwickey. "Most dermatologists would not recommend it for their psoriasis patients until more research has been done on it."