In contact irritant dermatitis the substance that damages the skin is known as the irritant. A highly irritant substance is known as a corrosive. Irritant dermatitis makes up about 80% of contact dermatitis. The other 20% is allergic.

There are several ways that skin damage can be caused.

  • Detergents, soaps such as in repeated hand washing or the use of solvents can remove the protective oily layer and so leave the skin exposed to damage.
  • Physical damage such as friction, minor cuts for example from fibre glass and grazes can breakdown the protective layer and allow substances access.
  • Chemical such as acids or alkalis can burn the layer.

Irritation is analogous to a chemical burn. It acts by eroding or burning the outer protective layers of the skin. Irritant contact dermatitis usually occurs only on the parts of the body in direct contact with the irritant substance e.g. hands, forearms, face. 

Common irritants are wet work, cutting oils, solvents and degreasing agents which remove the skins outer oily barrier layer and allow easy penetration of hazardous substances, alkalis and acids (see Table 1). Wet cement coming into contact with exposed feet and hands is a particular example of a skin irritant.