Allergic contact dermatitis - Anogenital in
Contact dermatitis presents as either allergic or irritant in etiology. While irritant contact dermatitis represents the direct toxic effect of an offending agent on the skin, allergic contact dermatitis (ACD) represents a delayed-type (type IV) hypersensitivity reaction that occurs when allergens activate antigen-specific T cells in a sensitized individual. Consequently, whereas irritant contact dermatitis can occur after one exposure to the offending agent, ACD typically requires repeat exposures before an allergic response is noted. ACD can occur 24-48 hours after exposure to the offending agent.
ACD can occur in response to topical agents, systemic exposure via ingestion, or innocuous transfer of the culprit agent via the fingertips.
Use of soap, topical anesthetic agents, spermicides, rubber accelerators found in condoms, and topical steroids have all been reported to cause ACD in the genital area. Lipstick-induced penile dermatitis has not been reported but is noted as a theoretical concern for men sensitive to octyl gallate.
Passive transfer of poison ivy resin has been implicated in penile ACD.
L23.9 – Allergic contact dermatitis, unspecified cause
40275004 – Contact dermatitis
Differential Diagnosis & Pitfalls
- Cellulitis – Plaque margins in cellulitis are often less distinct than those of contact dermatitis. The plaques of contact dermatitis are sharply demarcated and frequently take on bizarre geometric shapes and patterns.
- Lichen simplex chronicus
- Contact urticaria
- Herpes virus infection
- Seborrheic dermatitis
- Tinea cruris
- Fixed drug eruption
- Red scrotum syndrome
- Zoon balanitis
- Lichen planus
- Reactive arthritis (Reiter syndrome)
- Extramammary Paget disease
Drug Reaction Data