Irritation and staining by dithranol (anthralin) and related compounds. V. Short-contact and tape-stripping experiments with dithranol and butantrone.

Dithranol (D) and butantrone (BD) were compared as regards irritation and staining in conditions resembling short-contact therapy. Nine psoriatics were tested with 0.5% D and 0.66% BD using exposures of 20 min and 3 h. Partial removal of the horny layer by 15 tape strippings before and after the exposure resembled the impaired barrier of lesions and posttreatment washing, respectively. Development of erythema and staining, and alterations in blood flow were followed for 7 days. In the unstripped skin, D caused after 20 min exposure within 3 days a faint but defined erythema and increase in blood flow, and within 7 days a brownish hue. Irritation was suppressed by stripping after 20 min exposure. After 3 h contact, irrespective of stripping, much stronger irritation and staining developed. BD caused no staining after 20 min of exposure and little if any erythema. After 3 h contact, it caused only minimal staining and markedly less irritation than equimolar D.