Epidemiology
Etiology
Pathophysiology
Allergic contact dermatitis is an example of a type IV hypersensitivity reaction.
Presensitized CD4+ T cells recognize antigens on antigen-presenting cells, leading to the release of inflammatory cytokines, while presensitized CD8+ T cells recognize antigens on somatic cells, leading to cell-mediated cytotoxicity.
- First contact with allergen → sensitization
- Repeated contact with allergen → development of a rash after 12–48 hours
Clinical features
- Intensely pruritic erythematous papules
- Vesicles with serous oozing in more severe cases
Tip
Contact dermatitis due to poison oak, poison ivy, or poison sumac is the most likely cause in a patient presenting with erythematous, pruritic, and burning skin lesions in a linear pattern that appear 24 hours after a camping trip.