Increased gut permeability to macromolecules is thought to be an important factor in the development of food hypersensitivity. The latter can develop in the course of acute gastroenteritis and could play a role in infantile eczema. We studied gut permeability in 10 normal adults, 11 control children, 7 children with acute gastroenteritis, and 8 patients with infantile eczema, making use of [51Cr]EDTA as probe molecule. [51Cr]EDTA was given orally (50-100 microCi); 24-h urinary excretion of [51Cr]EDTA was measured and expressed as a percentage of the oral dose. Mean and standard error were 2.35 +/- 0.24, 2.51 +/- 0.21, 9.96 +/- 3.44, and 10.90 +/- 2.05 in normal adults, control children, and gastroenteritis and eczema patients, respectively. Differences between controls and either gastroenteritis (p less than 0.001) or eczema (p less than 0.001) patients are significant. Our results support the hypothesis that increased gut permeability could play a role in food hypersensitivity.