A dermatotoxin or dermatoxin is a toxic chemical that damages skin, mucous membranes, or both, often leading to tissue necrosis. Dermatoxins can be drugs, natural chemicals, or synthetic chemicals.

The severity of the effects of a dermatoxic agent is strongly dependent on the dose, route of exposure, rate at which it spreads, and the health of the afflicted individual.

It can produce allergic contact dermatitis, changes that lead to skin cancer, chemical burns, irritant dermatitis, photodermatitis, phototoxicity, changes to pigmentation, and urticaria.