Contact Dermatitis — SCE Dermatology MCQ

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EasyInflammatory DermatosesContact DermatitisSCE Dermatology

A 45-year-old woman with suspected allergic contact dermatitis to her new earrings undergoes patch testing with nickel sulfate 5% in petrolatum. At 48 hours, the test site shows erythema, infiltration, papules, and vesicles. How is this graded on the ICDRG scale?

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Correct answer: B — Strong positive (++)

ICDRG patch test reading scale: (-) = negative (no reaction); (+/-) = doubtful (faint macular erythema only); (+) = weak positive (erythema, infiltration, possibly papules); (++) = strong positive (erythema, infiltration, papules, vesicles); (+++) = extreme positive (bullous reaction). The described reaction (erythema + infiltration + papules + vesicles) corresponds to a strong positive (++) reaction. Irritant reactions (IR) show burning rather than itching, with sharp-bordered erythema, pustules, or necrosis without infiltration. Distinguishing allergic from irritant reactions requires experience and may benefit from repeat testing.

Reference: BAD 2017 Contact Dermatitis Guidelines; ICDRG