Contact allergy
| Contact dermatitis | |
|---|---|
 |
|
| Rash resulting from skin reactions. | |
| Classification and external resources | |
| Specialty | Dermatology |
| ICD-10 | L25.9 |
| ICD-9-CM | 692.9 |
| DiseasesDB | 29585 |
| MedlinePlus | 000869 |
| eMedicine | emerg/131 ped/2569 oph/480 |
| MeSH | D003877 |
Contact dermatitis is a type of inflammation of the skin.
It results from either exposure to allergens (allergic contact dermatitis) or irritants (irritant contact dermatitis). Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can often be supported by patch testing.
Contact dermatitis is a localized rash or irritation of the skin caused by contact with a foreign substance. Only the superficial regions of the skin are affected in contact dermatitis. Inflammation of the affected tissue is present in the epidermis (the outermost layer of skin) and the outer dermis (the layer beneath the epidermis).
Contact dermatitis results in large, burning, and itchy rashes. These can take anywhere from several days to weeks to heal. This differentiates it from contact urticaria (hives), in which a rash appears within minutes of exposure and then fades away within minutes to hours. Even after days, contact dermatitis fades only if the skin no longer comes in contact with the allergen or irritant. Chronic contact dermatitis can develop when the removal of the offending agent no longer provides expected relief.
Irritant dermatitis is usually confined to the area where the trigger actually touched the skin, whereas allergic dermatitis may be more widespread on the skin. Symptoms of both forms include the following:
While either form of contact dermatitis can affect any part of the body, irritant contact dermatitis often affects the hands, which have been exposed by resting in or dipping into a container (sink, pail, tub, swimming pools with high chlorine) containing the irritant.
Common causes of allergic contact dermatitis include: nickel allergy, 14K or 18K gold, Balsam of Peru (Myroxylon pereirae), and chromium. In the Americas they include the oily coating from plants of the Toxicodendron genus: poison ivy, poison oak, and poison sumac. Millions of cases occur each year in North America alone. The alkyl resorcinols in Grevillea banksii and Grevillea 'Robyn Gordon' are responsible for contact dermatitis.Bilobol, another alkyl resorcinol found in Ginkgo biloba fruits, is also a strong skin irritant.
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