Diagnosis: Contact dermatitis
Foot pad dermatitis and hock burns on a broiler chicken. Clinical photograph sourced from Wikimedia Commons (Public domain). Attribution: National Organic Standards Board.
Acute: erythematous, edematous plaques with vesicles, weeping in geometric or linear patterns corresponding to contact area. Chronic: lichenified, dry, fissured plaques. Distribution is the most important diagnostic clue — pattern mirrors the contactant.
Detailed occupational history essential. Common allergens: nickel (jewelry), fragrance, preservatives, rubber accelerators, hair dye (PPD), plants (poison ivy/oak — urushiol). Onset 24-72 hours after exposure in allergic CD, immediate in severe irritant CD.
Allergen/irritant avoidance (most important). Acute: cool compresses, topical corticosteroids (mid-high potency), oral prednisone taper for severe/widespread. Chronic: emollients, topical corticosteroids. Patch testing for definitive allergen identification.
Atopic dermatitis, Tinea, Psoriasis, Nummular dermatitis, Drug eruption, Scabies
Patch testing (T.R.U.E. Test or custom panels) is the gold standard for identifying allergens. Poison ivy/oak dermatitis is the most common allergic CD in North America. The pattern of distribution is more diagnostic than the morphology.
Tags: contact dermatitis, allergic, irritant, occupational, eczema