Definition of Contact dermatitis:

Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating substance.

See also: Poison ivy - oak - sumac

Causes, incidence, and risk factors:

Contact dermatitis is an inflammation of the skin caused by direct contact with an irritating or allergy-causing substance (irritant or allergen). Reactions may vary in the same person over time. A history of any type of allergies increases the risk for this condition.

Irritant dermatitis, the most common type of contact dermatitis, involves inflammation resulting from contact with acids, alkaline materials such as soaps and detergents, solvents, or other chemicals. The reaction usually resembles a burn.

Allergic contact dermatitis, the second most common type of contact dermatitis, is caused by exposure to a substance or material to which you have become extra sensitive or allergic. The allergic reaction is often delayed, with the rash appearing 24 - 48 hours after exposure. The skin inflammation varies from mild irritation and redness to open sores, depending on the type of irritant, the body part affected, and your sensitivity.

Overtreatment dermatitis is a form of contact dermatitis that occurs when treatment for another skin disorder causes irritation.

Common allergens associated with contact dermatitis include:

• Poison ivy, poison oak, poison sumac
• Other plants
• Nickel or other metals
• Medications
  • Antibiotics, especially those applied to the surface of the skin (topical)
  • Topical anesthetics
  • Other medications
• Rubber or latex
• Cosmetics
• Fabrics and clothing
• Detergents
• Solvents
• Adhesives
• Fragrances, perfumes
• Other chemicals and substances

Contact dermatitis may involve a reaction to a substance that you are exposed to, or use repeatedly. Although there may be no initial reaction, regular use (for example, nail polish remover, preservatives in contact lens solutions, or repeated contact with metals in earring posts and the metal backs of watches) can eventually cause cause sensitivity and reaction to the product.

Some products cause a reaction only when they contact the skin and are exposed to sunlight (photosensitivity). These include shaving lotions, sunscreens, sulfa ointments, some perfumes, coal tar products, and oil from the skin of a lime. A few airborne allergens, such as ragweed or insecticide spray, can cause contact dermatitis.