The cutaneous reaction to staphylococcal protein A in normal subjects and patients with atopic dermatitis or psoriasis

Intradermal testing with the staphylococcal cell wall component, protein A, in healthy volunteers and in patients with atopic dermatitis and psoriasis produced a range of responses but in all groups there was an immediate weal and flare response. There was marked individual variation in subsequent erythema, but the patients with atopic dermatitis had less erythema at 15 min and 24 h than normal or psoriatic individuals. The greatest erythematous reaction at 48 h was seen in patients with psoriasis.