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Contact dermatitis
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<p>Contact dermatitis is a type of acute or chronic <a href="/facts/Inflammation/Ura86MIy">inflammation</a> of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red <a href="/facts/Rash/W97qGpq6">rash</a>, bumps, <a href="/facts/Blister/qGhqaeQV">blisters</a>, or swelling. These rashes are not contagious or life-threatening, but can be very uncomfortable. </p><p>Contact dermatitis results from either exposure to <a href="/facts/Allergen/bnM4cttq">allergens</a> (<a href="/facts/Allergic_contact_dermatitis/cNyAKVe7">allergic contact dermatitis</a>), or <a href="/facts/Irritation/vGtMyXUR">irritants</a> (<a href="/facts/Irritant_contact_dermatitis/DPn2WxB9">irritant contact dermatitis</a>). Allergic contact dermatitis involves a delayed type of hypersensitivity and previous exposure to an allergen to produce a reaction. Irritant contact dermatitis is the most common type and represents 80% of all cases. It is caused by prolonged exposure to irritants, leading to direct injury of the <a href="/facts/Epidermis/JvRABubP">epidermal cells</a> of the skin, which activates an <a href="/facts/Immune_response/dtLulqIy">immune response</a>, resulting in an inflammatory cutaneous reaction. <a href="/facts/Phototoxicity/9MjkWKEM">Phototoxic</a> dermatitis occurs when the allergen or irritant is activated by sunlight. Diagnosis of allergic contact dermatitis can often be supported by <a href="/facts/Patch_test/TJaD3ERo">patch testing</a>. </p>