TY - CHAP M1 - Book, Section TI - Contact Dermatitis A1 - Bogle, Melissa A. A1 - Militello, Giuseppe A1 - Jacob, Sharon E A2 - Ali, Asra Y1 - 2015 N1 - T2 - McGraw-Hill Education Specialty Board Review Dermatology: A Pictorial Review, 3e AB - Inflammatory response of the skin to an antigen (allergen) or irritantAllergic contact dermatitis (ACD)Delayed type hypersensitivity reaction (type IV)Dermal Dendritic cells play a central role in processing and presenting antigen complexes in the sensitization phaseIndividuals previously sensitized to the allergen can develop a cutaneous response with subsequent exposure to the allergen. These responses can be incrementally more severe with each exposure.Common allergens include plants from the Toxicodendron genus (e.g., poison ivy), nickel sulfate, fragrances, preservatives, and rubber additivesAcute ACD: lesions appear within 24 to 96 hours of exposure to the allergen in sensitized individualsIrritant contact dermatitis (ICD)Irritants are cytotoxic to the keratinocyte, disrupt the lipid architecture, and promote the release of inflammatory mediatorsICD will only occur in areas of the skin that has been in direct contact with the offending chemical agentSubsequent inflammatory response in the dermisTwo types:– Mild irritants: require prolonged or repeated exposure before inflammation is noted (e.g., soap)– Strong irritants: strong acids, alkalis, can produce immediate reactions similar to thermal burnsClinical PresentationAcute contact dermatitis: clear fluid–filled vesicles or bullae that appear on bright red edematous skin, pruritic. ICD generally occurs within the area of contact with the chemical, whereas ACD can extend beyond the borders of the contact areaSubacute contact dermatitis: less edema and formation of papules, pruriticChronic contact dermatitis: minimal edema, scaling, skin fissuring, and lichenificationHistologyDermis with perivascular lymphocytes and other mononuclear cells and epidermal spongiosis are seen in ACD. Cytotoxicity more commonly seen in ICDChronic ACD: acanthosis with hyperkeratosis and parakeratosis. Difficult to distinguish, clinically and histologically, allergic contact from irritant contact dermatitis in the chronic phase SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - dermatology.mhmedical.com/content.aspx?aid=1176105268 ER -