Contact dermatitis is inflammation of the skin caused by contact with a substance that causes an allergic reaction. A minor case of contact dermatitis may cause mild redness of the skin or a rash of small red bumps, while a more severe reaction may cause swelling, redness, and larger blisters.
A rash usually starts about 48 hours after exposure to the irritating substance. Common causes of contact dermatitis include:
Poisonous plants, such as poison ivy, oak, or sumac.
Soaps, detergents, shampoos, perfumes, cosmetics, or lotions.
Jewellery or fabrics.
New tools, toys, appliances, or other objects.
The location of the rash may provide a clue about the cause.
Contact dermatitis does not usually occur with the first exposure to the irritating substance (allergen). After a reaction to the substance occurs for the first time, a rash can occur in response to even very small amounts of the substance.
Adam Husney, MD - Family Medicine & Brian O'Brien, MD, FRCPC - Internal Medicine & Martin J. Gabica, MD - Family Medicine & Amy McMichael, MD - Dermatology