Contact depigmentation caused by an azo dye in alta.

Alta, a scarlet-red solution used by some Indian women as a cosmetic to colour their feet, was found to be associated with depigmentation at the site of application. Chromatographic and spectroscopic analysis of 3 brands of alta confirmed the presence of 2 dyes: Crocein Scarlet MOO (CSM) (brilliant crocein) and rhodamine B (tetraethyl rhodamine). Patch testing produced depigmentation at the site of application of alta, CSM and para-phenylenediamine (PPD). Although PPD has been reported to produce leukoderma, azo dyes have not previously been reported as depigmenting agents.