Dermatoxin

A dermatoxin (from "derma", the Greek word for skin) 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.