The effect of bacterial infection in the worsening of atopic dermatitis: correlations with humoral immunologic patterns.

The contribution of secondary infection to severity and tendency to relapse in atopic dermatitis during childhood has been assessed. A total of 57 children aged between 4 months and 14 years were followed for an average of 4.73 months. A secondary infection was diagnosed in 22 (31.4%) of 70 relapses, since the lesions only subsided with antibiotics active on the bacteria isolated from the skin, usually a coagulase-positive Staphylococcus aureus. The eczema was more severe at presentation and hypogammaglobulinemia G more often found in those children who were more susceptible to secondary infections. The hypogammaglobulinemia G was present in 13 out of the 57 patients, but it normalized with age and was not correlated with IgE levels. In the children in whom the relapse or the worsening of the eczema could be attributed to secondary infection because of the positive response to the antibiotic treatment, the lesions had the appearance of pustules or showed more exudation, although in some cases only the worsening of the erythema and itching was observed. A secondary bacterial infection should be considered a likely cause of relapse or worsening of atopic dermatitis. Furthermore it may be that, at least in first year of life, hypogammaglobulinemia G is part of an immunologic impairment of atopic dermatitis which favors the susceptibility to secondary infections.