Drugs that are used to treat hyperkeratosis, a thicken-ing of the stratum corneum, are called keratolytics. Examples of these agents are salicylic acid, urea, lactic acid, and colloidal or precipitated sulfur. The precise mechanisms by which these agents treat hyperkeratosis are not known. Presumably, a common property is the ability to denature keratin, the major structural protein of the epidermis. Other beneficial effects vary among the different drugs. All of them have antimicrobial or
antiparasitic properties. Salicylic acid is a potent antiin-flammatory agent. Urea is highly hygroscopic, enhanc-ing the ability of tissue to absorb and retain water. Keratolytics are especially useful for treatment of corns and calluses, warts, palmoplantar keratodermas, ich-thyoses, and psoriasis. When used in conjunction with topical steroids for treatment of psoriasis, keratolytics enhance the steroid’s penetration. Urea may also be used for chemical avulsion of dystrophic nails.
Selenium sulfide is a cytostatic and sporicidal agent available without prescription in a variety of shampoos and lotions for treatment of scalp seborrheic dermatitis. Higher concentrations are available by prescription for the treatment of pityriasis versicolor, which is caused by the yeast M. furfur, and tinea capitis.