A rash called contact dermatitis may occur when the skin comes in direct contact with an irritating or allergy-causing substance. This type of skin inflammation is very common and accounts for 85 to 95 percent of workplace-related skin diseases, notes the World Allergy Organization. Symptoms may include redness, localized swelling, lesion or rash. In chronic cases, the skin may become scaly, raw or thickened.
Irritants
About 80 percent of contact dermatitis occurs when a strong chemical or substance causes direct damage to the skin, resulting in burning and a painful, rather than an itchy, rash, describes the Merck Manuals Online Medical Library. The skin damage may occur immediately in some cases, and after prolonged or repeated contact in others. Common irritants include acids; alkalies, such as drain cleaners, strong soaps and detergents; solvents like acetone polish nail remover; and certain plants such as poinsettias and pepper.
Allergy-causing Substances
People who are extra sensitive or allergic may experience contact dermatitis when exposed to allergy-causing substances. In these cases, the immune system mounts a reaction that results in a very itchy rash that appears 4 to 24 hours after exposure, but may even occur 3 to 5 days later, notes Merck. MedlinePlus lists a variety of allergens that causes contact dermatitis including nickel, poison ivy, oak and sumac, latex, cosmetics, fragrances and perfumes, and certain medications.
Photo-reacting Substances
Some products cause contact dermatitis when applied to the skin and then exposed to the sun. According to the World Allergy Organization, chemical photosensitizers such as psoralens, naturally found in plants like figs, celery and parsley, can produce contact dermatitis resembling sunburn. Furocoumarins, found in lime juice, can also cause a non-allergic blistering rash, according to a case reported in the July 5, 2007 edition of the "New England Journal of Medicine." Photoallergic substances may also be found in sunscreens, aftershave lotions, sulfa ointments, perfumes and coal tar products, notes MedlinePlus.
