Food hypersensitivity is reported to play an immunopathogenic role in atopic dermatitis in approximately one-third of children. In 320 selected children with moderate to severe atopic dermatitis, 63% of children were found to have food hypersensitivity by double-blind placebo-controlled food challenges. Both IgE-mediated mast cell and mononuclear cell activation appear responsible for the eczematous lesions resulting from ingestion of food allergens.