Although the deleterious effect of Staphylococcus aureus on atopic eczema is well recognized, the mechanism of this effect may be more complex than pyogenic infection alone. We have shown that the majority of S. aureus cultures isolated from atopic eczema produced exotoxins with superantigenic properties, although this was no more frequent than in a control group, and was not restricted to one particular superantigen. However, the widespread nature of staphylococcal infections in atopic eczema indicates that sufficient superantigen may be released to cause T-lymphocyte activation, cytokine release, and mast cell degranulation. These mechanisms could, in part, explain the exacerbations of atopic eczema associated with S. aureus infection.