Irritancy of dithranol in normally pigmented and depigmented skin of patients with vitiligo.

In order to ascertain the extent to which the pigmentary system plays a protective role in dithranol-induced irritancy, a within-subject comparison was carried out between normally pigmented and depigmented skin of patients with vitiligo. In open patch tests, various concentrations of dithranol in a cream base were applied to the normally pigmented and depigmented skin of 6 patients with vitiligo. The responses were assessed 48 h after application. A mild to moderate inflammation occurred in the pigmented and depigmented skin and no statistically significant difference was shown between the two test areas. The present study does not support the hypothesis that the pigmentary system might be involved in dithranol-induced irritancy.