Occlusive irritant dermatitis: when is "allergic" contact dermatitis not allergic?

CASE 1: A 38-year-old teacher presented with a 3- to 4-week history of a linear, erythematous, vesicular, and pruritic eruption of her left wrist. She had been wearing a new elastic bracelet for 4 weeks before the onset of her eruption. Although there was no history of allergy to rubber products or jewelry, an allergic contact dermatitis to rubber was suspected. Patch testing to rubber chemicals and the elastic bracelet revealed no reactions at 48, 72, and 96 hours. She stopped wearing the bracelet and used a corticosteroid cream with rapid resolution of the problem. The patient resumed wearing the bracelet, and there has been no recurrence in the past 2 months. CASE 2: A 12-year-old boy presented with a 1-month history of an itchy, scaly, erythematous 1-cm patch over the midline of his lower lip. The patient complained of tiny blisters initially with persistent erythema, mild scaling, and associated pruritus. The patient plays the saxophone and he had been practicing more intensely (3 to 4 h/d) for a musical competition. Allergic reaction to his wood reed was suspected, but patch testing with a moistened portion of his reed and reed shavings in a drop of water revealed no reaction at 48 and 72 hours. Treatment with hydrocortisone 1% cream bid for 3 days led to complete resolution of the dermitis and pruritus. Playing the saxophone 1 h/d has not led to any recurrence. CASE 3: A 33-year-old woman presented with erythema, scaling, and pruritus of 1 month's duration beneath her engagement and wedding rings, which were worn together on her left fourth finger (Figure 3). Although she had no history of previous sensitivity to earrings, watch clasp, blue jean rivets, or other jewelry, allergic contact dermatitis to nickel was suspected. Patch testing was performed to the common metal allergens nickel, cobalt, chromium, and gold. Readings at 48 hours and 1 week revealed no positive reactions. The patient wore her rings on the right hand for 1 week and used fluocinonide 0.5% cream twice daily for 1 week with resolution of the dermatitis. She has subsequently begun wearing the rings again on her left hand with care to dry her hands and rings after washing, and there has been no recurrence of her dermatitis.