The treatment of hypermelanosis with 4-isopropylcatechol.

Over the past 6 years sixty-eight patients have been treated with 1% or 3% 4-isopropylcatechol (4-IPC). Fifty-four had melasma, the others a variety of disorders of pigmentation. Two-thirds of the patients were significantly improved. Twenty patients had skin irritation due to 4-IPC and four developed an allergic contact dermatitis. One patient developed confetti-like areas of depigmentation in the 4-IPC-treated areas. Light and electron microscopic studies showed that in the 4-IPC-treated areas there was a loss and damage of the melanocytes, but the keratinocytes and Langerhans cells were unaffected. Melanosomal complexes containing many melanosomes were frequently found in the keratinocytes of the 4-IPC-treated negro skin. 4-Isopropylcatechol is a potent depigmenting agent and is of use in the topical therapy of selected patients with hypermelanosis. However, like other substituted phenols and hydroquinone it is irritant to the skin and should be used with caution.