Relevance of milk- and egg-specific IgG4 in atopic eczema.

In a substantial proportion of atopic eczema patients clinical sensitivity to food is not confirmable by either skin prick test or IgE RAST. The diagnosis of provocative food factors in this condition is, therefore, highly dependent on dietary manipulations which are time consuming and sometimes dangerous. In an attempt to find an alternative laboratory procedure we have questioned the clinical relevance of specific IgG4 measurement in the sera of these patients in the light of previous reports demonstrating raised total serum IgG4 in patients with atopic eczema. Thus, a highly reliable ELISA was developed to measure IgG4 specific to 3 cow's milk proteins and 2 hen's egg proteins in the sera of milk- and egg-allergic eczema patients and non-eczematous controls. The study provides clear evidence showing that the detection of milk- and egg-specific IgG4 in atopic eczema patients has no clinical value.