Of the various available chemical agents that affect the process of melanin pigmentation only two are of practical therapeutic value: hydroquinone and psoralen derivatives.
Hydroquinone, a known inhibitor of the tyrosine-tyrosinase system, is a moderately effective topical agent for decreasing hypermelanosis in all races. A 2% cream of stabilized hydroquinone effectively decreased hypermelanosis without untoward effects in 63.5% of the 93 patients studied.
The history, sources, chemistry, and photobiology of the psoralens are described.
A decade of experience indicates that early misgivings that psoralen derivatives might induce serious untoward effects were unjustified.
The larger doses of psoralens advocated by El Mofty in Egypt for the treatment of vitiligo appear to be more effective than the smaller doses generally advocated by others. Because no more satisfactory agents are yet available for the treatment of vitiligo, the use of psoralen derivatives is recommended in some cases of vitiligo.