The avoidance of incriminated foods is one of the principal therapies for atopic dermatitis (AD). Recently, interferon (IFN)-γ therapy has been tried in AD with limited success. The necessity of diet therapy for the success of IFN-γ therapy in AD was evaluated. A total of 524 AD patients participated in this study and 316 patients among them were entered into open food challenge tests. As the first step, an elimination diet was administered to 43 AD patients and 30 AD patients were enrolled as an untreated control group. As the second step, 45 AD patients were treated by both IFN-γ therapy and elimination diet alone, 30 AD patients by elimination diet alone, 50 AD patients by IFN-γ therapy, and 43 AD patients as controls. Clinical severity reduced significantly by using only the elimination diet in 58.1% patients with varying degrees of AD. Elimination diet improved the clinical results of IFN-γ therapy in AD. In regard to the food challenge test, 77.8% of AD patients showed an adverse reaction to at least one food. Diet therapy itself had therapeutic effects on AD and an elimination diet might be essential for the success of IFN-γ therapy in AD.