Contact Dermatitis Causes

There are 2 types of contact dermatitis: allergic and irritant.

• Like all allergic reactions, allergic contact dermatitis results from a reaction of the immune system.
  • The immune system overreacts to the foreign substance, usually an animal or vegetable protein. The immune system is activated to produce antibodies against this allergen. This overreaction is often called a hypersensitivity reaction.
  • The antibody, called immunoglobulin E or IgE, is stored on special cells called mast cells.
  • When they come in contact with the allergen, the antibodies promote release of chemicals and hormones called "mediators." Histamine is an example of a mediator.
  • It is the effects of the mediators that cause the symptoms of the allergic reaction, in this case an itchy rash.

• In allergic contact dermatitis, then, you have a skin reaction to something that has touched your skin at that site. Unlike most allergic reactions, the trigger is external rather than internal.
  • Your initial exposure does not cause a rash. However, it sensitizes your skin so that you will react to the next exposure. If you seem to react the first time you are exposed to an agent, you probably were exposed before without knowing.
  • Common plant allergens that cause dermatitis include poison ivy, poison oak, and poison sumac.
  • Many other substances can cause allergic reactions, including hair dyes or straighteners; the metal nickel, which is found in jewelry and belt buckles; tanning agents in leather; latex rubber; and citrus fruit, especially the peeling.
  • The fragrances in soaps, shampoos, lotions, perfumes, and cosmetics can cause a reaction.
  • Even certain medications applied to the skin can cause dermatitis.

• Irritant contact dermatitis results from coming in contact with a substance that directly damages your skin.
  • The longer the substance remains on the skin, the more severe the reaction.
  • Many chemicals, including industrial cleaning products and solvents, can cause this condition.
  • Household cleaners such as detergents can also cause dermatitis.

• People with other skin conditions, such as eczema, are most likely to develop contact dermatitis.