The purpose of the study was to investigate whether the duration of sensitization to food allergens during early childhood is related to later development of IgE mediated hypersensitivity to inhalant allergens and of allergic rhinitis and asthma in 5-year-old children and whether long-lasting food-sensitization may be used to predict subsequent allergic airway diseases. Five hundred and eight children of a prospective birth cohort study with available serum samples at one and two years of age were included and followed up until five years of age. Specific sensitization to food and inhalant allergens and the occurrence of subsequent allergic airway diseases were determined. Children with a long-lasting sensitization to food allergens (persistently sensitized for more than one year) produced significantly higher total IgE and specific IgE levels than children who were only transiently food-sensitized by two years of age. Children persistently sensitized to food had a 3.4 fold higher risk of developing allergic rhinitis and a 5.5 fold higher risk of developing asthma than infants who were only transiently food sensitized. Persistent food sensitization in combination with a positive atopic family history was a strong predictor for the development of allergic rhinitis and asthma at five years of age. The risks for these children are up to 50%, and 67% respectively. Persistently detectable sensitization to food over more than one year in early childhood is a strong prognostic factor for subsequent allergic airway disease. Persistently food-sensitized children especially in atopic families have to be regarded as a high-risk group and should be considered for preventive measures against respiratory atopy.