BACKGROUND: Sensitization to peanut has seldom been investigated in Sweden. Therefore, all IgE-specific tests for peanut during a 5-year period were reviewed to study the relation between the levels of specific IgE antibody to peanut and age, sex, symptoms, and other atopic manifestations. METHODS: All serum samples were analyzed for IgE antibodies to peanut in relation to sex, age, clinical reactions, and other food allergens. A subgroup was asked to answer a questionnaire about symptoms and atopic manifestations in relation to IgE antibody levels. RESULTS: During the study period, 2417 tests were made for peanut. There was an increased prevalence of detectable IgE antibodies during the years studied. More than 80 individuals under 2 years of age were sensitized to peanut. In the subgroup, individuals with detectable IgE antibodies reported a shorter reaction time after eating peanuts than individuals with normal IgE antibody levels (P