Background There is a paucity of information on food hypersensitivity (FHS) among teenagers. Objectives We sought to investigate the sensitization rates, perception of FHS, food avoidance, and FHS assessed by means of food challenges among teenagers. Methods This cohort study recruited 757 eleven-year-olds and 775 fifteen-year-olds in the United Kingdom. Sensitization rates, reported rates of FHS, and rates of food avoidance were measured. The prevalence of FHS was established by using food challenges. Results The prevalence of reported FHS among the 11- and 15-year-old cohorts was 11.6% (90/775) and 12.4% (94/757), respectively. One hundred twenty-two (15.7%) and 142 (18.7%) of the 11- and 15-year-olds reported they were avoiding some food. The rates of sensitization to the food allergens were 5.1% (36/699) and 4.9% (32/649) for the 11- and 15-year-olds, respectively. FHS was confirmed in 8 (1.0%) 11-year-old children and 8 (1.0%) 15-year-old children by means of open food challenge and in 1 (0.1%) 11-year-old and 4 (0.5%) 15-year-olds by means of double-blind, placebo-controlled food challenge. The prevalence of FHS, as confirmed by using open food challenges and positive skin prick test responses plus a history of adverse reactions, was 18 (2.3%) of 775 in the 11-year-old cohort and 17 (2.3%) of 757 in the 15-year-old cohort. Conclusions The rate of reported FHS was significantly more than sensitization to the predetermined allergens (odds ratio, 2.17; 95% CI, 1.47-3.18; P < .001 in the 11-year-olds; odds ratio, 2.73; 95% CI, 1.81-4.13; P < .001 in the 15-year-olds). By means of objective assessment, 2.3% of both 11- and 15-year-old children had FHS, with the majority showing immediate reactions.