A 31-year-old Caucasian woman presented with a 20-year history of presumed atopic dermatitis. She complained of severe pruritus and the presence of extensive patches of erythema and scale. Her previous treatments included: multiple topical corticosteroids, tacrolimus 0.1% ointment, pimecrolimus 1% cream, and cyclosporine with no improvement of her symptoms. Her past medical history was unremarkable and she was on no other oral medications, including over-the-counter products. On physical examination, multiple erythematous, scaly patches were present on the chest, abdomen,back, and upper extremities. Lichenification of both antecubital fossa was present. Extensive excoriations on her arms and abdomen were also noted. Although the patient had a long-standing history of presumed atopic dermatitis, she had never undergone a skin biopsy. A skin biopsy was performed which demonstrated a perivascular lymphocytic infiltrate with eosinophils and dermal edema (Figures 1, 2). The biopsy was suggestive of possible hypersensitivity dermatitis. The patient then underwent patch testing. The following patch tests were applied to normal back skin using IQ chambers:North American Contact Dermatitis Group (NACDG) expanded standard, textile, fragrance trays, and ingredients found in her products (Chemotechnique, Malmo, Sweden). A total of 89 patches were applied, removed at 48 hours, and read both at 48 and 96 hours. At 48 hours, a total of 70 allergens were positive, 69 of those allergens were in a petrolatum vehicle. There were 50, 3+ reactions to sites of allergens in petrolatum (Figure 3). There were only two sites with petrolatum that were negative: budesonide (a corticosteroid) and melamine formaldehyde. In contrast, all of the sites where there were allergens in liquid vehicles were negative, with the exception of a 1+ reaction to cocamidopropyl betaine. At 48 hours,four additional patch tests were applied to plain petrolatum. Two of these patches were in plastic IQ chambers and two in aluminum Finn Chambers. At 48 hours, all four of the sites showed 3+ reactions (Figure 4). By 96 hours, all of the patch test sites that were positive at 48 hours, and much of the surrounding skin, showed a diffuse "angry back" reaction, which made an accurate 96-hour reading impossible.