Poison ivy, poison oak, and poison sumac contain urushiol. An itchy and inflamed rash can result when urushiol touches your skin due to an immune response. The resulting condition is contact dermatitis.
Reactions may vary in the same person over time. A history of any type of allergies increases the risk for this condition.
The 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
Nickel or other metals
Antibiotics, especially those applied to the surface of the skin (topical)
Rubber or latex
Fabrics and clothing
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.