indigo naturalis

**Indigo naturalis** is a traditional Chinese herbal drug and plant-derived topical/oral medicinal substance prepared from indigo-containing plants such as *Baphicacanthus cusia* and used clinically most prominently for inflammatory skin diseases and ulcerative colitis. In the provided sources, it has been studied as a **topical ointment/oil extract** for plaque psoriasis, nail psoriasis, and atopic dermatitis, and as an **oral herbal medicine** for ulcerative colitis. Its pharmacology appears to be multi-component and polypharmacologic rather than driven by a single defined target: major constituents include **indirubin**, **tryptanthrin**, and **indigo**; published mechanistic work links topical activity in psoriasis to **downregulation of the IL-17 pathway**, with tryptanthrin showing anti-IL-17-associated effects in keratinocyte assays, while oral activity in ulcerative colitis has been linked to **aryl hydrocarbon receptor activation** by indigo/indirubin. Clinical studies in the provided material report efficacy signals in psoriasis, nail psoriasis, atopic dermatitis, and treatment-refractory ulcerative colitis, generally with topical formulations appearing locally tolerable, though oral indigo naturalis has broader safety concerns in the literature and should not be conflated with the topical preparations.

Brand names

Lindioil

Other names

Qing Dai青黛青黛膏