Coal tar has antipruritic, keratoplastic and keratolytic properties. It slows down excessive epidermal cell turnover and is often used topically either alone or in combination with other drugs (e.g. salicyclic acid, sulfur) in conditions such as dandruff, seborrheic dermatitis or psoriasis. Salicylic acid has a potent keratolytic action and a slight antiseptic action when applied topically. It softens and destroys the stratum corneum by increasing endogenous hydration which causes the horny layer of the skin to swell, soften, and then desquamate. At high concentrations, salicylic acid has a caustic effect. It also possesses weak antifungal and antibacterial activity.