Allergic Contact Dermatitis

Allergic Contact Dermatitis is a delayed hypersensitivity reaction caused by skin contact with an allergen, resulting in inflammation, redness, itching, and other skin irritations. The reaction typically appears 12-72 hours post-exposure and is diagnosed via history, physical exam, and patch testing.

Allergic Contact Dermatitis (ACD) is a type of delayed hypersensitivity reaction triggered by direct skin contact with an allergen. It is characterized by inflammation of the skin, manifesting as redness, itching, swelling, blistering, and scaling at the site of contact. The reaction typically develops 12-72 hours after exposure, depending on the degree of sensitization and allergen concentration. ACD is an acquired immune response, meaning it develops after repeated exposure to the allergen. Common allergens include poison ivy/oak/sumac, nickel, fragrances, preservatives, and certain medications applied topically. Chronic ACD can lead to lichenification (thickening of the skin) and persistent itching. Diagnosis is typically based on history, physical examination, and patch testing to identify the specific allergen.