ABSTRACT
Skin encounters substances with widely ranging toxicities. It must be remembered that many agents used in treatment, such as corticosteroids and salicylic acid, are systemically absorbed when placed on the skin and can cause systemic toxicity if large areas are treated. Agents that cause blistering are known as vesicants. Blister beetles release vesicants when crushed on the skin. Colloquially known as ‘Spanish fly’, the substance, unjustifiably, had the reputation of being an aphrodisiac. Chemical warfare agents include vesicants known as the mustards, which cross-link DNA, preventing cell division, and also cause severe blistering and erosion on contact with the skin. Some materials particularly irritate the hair follicles and stimulate the production of sticky horn, causing comedos and an acneiform folliculitis. Cocoa butter, thick, oily materials including paraffin waxes and substances such as isopropyl myristate are notorious for doing this in susceptible individuals.
