Keratolytics

Keratolytics are substances that promote the shedding of the outermost layer of the skin, the stratum corneum, by breaking down keratin or disrupting the intercellular connections between corneocytes. By thinning thickened skin and softening scales, they facilitate desquamation and easier removal of abnormal keratinized tissue. They are used to treat hyperkeratotic conditions such as plantar warts, calluses and corns, as well as certain dermatologic conditions where exfoliation is beneficial, including acne, psoriasis and ichthyosis.

Common keratolytics include salicylic acid, urea, glycolic and lactic acids, sulfur, and resorcinol. Salicylic acid dissolves the intercellular cement between keratinocytes, promoting gradual sloughing and penetration of other topical agents. Urea acts as both a keratolytic and a humectant, with higher concentrations producing more keratolysis and skin-softening. Alpha-hydroxy acids such as glycolic and lactic acids exfoliate by loosening desmosomal attachments and increasing turnover of the stratum corneum. Sulfur and resorcinol are also used for keratolytic purposes, though resorcinol can cause irritation and skin discoloration in some individuals.

Keratolytics are typically formulated for topical application as creams, gels, solutions, or patches and are used with occlusion in some regimens to enhance effect. Safety considerations include the potential for skin irritation, redness, dryness, or chemical burns, especially with higher concentrations or on sensitive skin. Systemic toxicity is rare but possible with extensive application, particularly in children or when large areas are treated. They should be avoided on broken skin, mucous membranes, or in certain populations (for example, during pregnancy) without medical supervision, and individuals with diabetes or peripheral vascular disease should use them under professional guidance for specific indications.