ContactDermatitis - Contact Dermatitis Definition Contact...

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Contact Dermatitis Definition Contact dermatitis is any inflammatory reaction of the skin that results from direct contact with an offending agent. Most cases of contact dermatitis can be classified as allergic contact dermatitis (ACD) or irritant contact dermatitis (ICD). Additional types of contact dermatitis can include photodermatitis and contact urticaria. Pathophysiology Pathophys of contact dermatitis overall: The main pathologic feature of contact dermatitis is intercellular edema of the epidermis. This initial reaction may result in intraepidermal vesicle and bullae formation in acute cases and papules, scaling, and lichenification in chronic cases. Within the dermal layer, various cells congregate around the dilated capillaries to aid in inflammatory response. Contact dermatitis is due to either allergic reaction or, more commonly, irritant exposure . Irritant Contact Dermatitis An irritant produces direct local cytotoxic effect on the cells of the epidermis as a result of direct injury to the skin, with a subsequent inflammatory response in the dermis It affects individuals exposed to specific irritants and generally produces a stinging or burning sensation within seconds of exposure . Alternatively, extended exposure to a mild irritant can cause a chronic form of ICD. In this case, dryness precipitates an erythematous state, which ultimately leads to cracking and the formation of painful fissures. Irritants (as small molecular weight haptens) form a complete antigen by binding to dermal proteins and causing a sensitization (of T lymphocytes) on first contact and an inflammatory response on subsequent exposure. Allergic Contact Dermatitis A cell-mediated type IV delayed hypersensitivity reaction results from specific antigens penetrating the epidermal skin layer.
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The antigen combines with a protein mediator and travels to the dermis, where T lymphocytes become sensitized. On the subsequent exposure to the antigen, the allergic reaction takes place. Only individuals previously sensitized to the contactant. Reexposure to sensitized antigens causes delayed hypersensitivity 13.6 cases per 1000 population Irritant contact dermatitis is common in occupations that involve repeated hand washing or repeated exposure of the skin to water, food materials, and other irritants. High-risk occupations include cleaning, hospital care , food preparation, and hairdressing. Hand-washing frequency of more than 35 times per shift was associated strongly with occupational hand dermatitis Climate/weather Low humidity and cold temperatures increase incidence of contact dermatitis. Race
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This note was uploaded on 02/18/2012 for the course PAS 600 - 601 taught by Professor Garrubba during the Fall '10 term at Chatham University.

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ContactDermatitis - Contact Dermatitis Definition Contact...

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