Development of atopic disease was prospectively studied in 148 children from birth to the age of 18 months and related to serum levels of IgG anti-IgE antibody. Children with a dual heredity of allergy, but remaining healthy, had significantly higher IgG anti-IgE levels at birth than children with a similar predisposition to allergy, who became allergic. Children with increased allergy risk, defined by elevated IgE levels at birth (>= 0.53 kU/l) and with probable allergy symptoms had also significantly higher IgG anti-IgE levels at birth than children of the same risk group, developing definite allergy. Independent of allergy risk, there was a significantly lower prevalence of atopic disease in children with cord serum levels of IgG anti-IgE above 350AU.1 than in children with lower levels. Additionally, we showed that the allergy predictive capacity of IgE levels in cord serum was slightly improved in specificity, sensitivity and efficiency by including not only the family history of allergy, but also cord serum levels of IgG anti-IgE. Our results thus raise the possibility that high levels of IgG anti-IgE protect children of increased allergy risk from early development of atopic disease and reduce the severity of symptoms.