Allergic Contact Dermatitis

• Usually involves Type IV reaction not just contact dermatitis
• Pruritic lesions with self-inflicted trauma
• At areas in contact with allergen
• Grossly:
  • Erythema, papules, +/- vesicles, exudation -> crusts
  • If chronic, lichenification, hyperpigmentation, alopecia
• Microscopically:
  • Spongiotic superficial perivascular dermatitis
  • Mononuclear cells
  • If chronic, epidermal hyperplasia
  • May involve eosinophils