Background Despite drug-related hypersensitivity reactions are an important health problem, epidemiologic data on drug allergy and hypersensitivity are limited, and studies including diagnostic work-up are scarce. The aim of this study was to determine the actual frequency of immediate type drug hypersensitivity using diagnostic tests in school children with parent-reported drug allergies. Methods This study involved three phases. The first phase is a survey of children with a mean age of 12.9yrs attending grades 68 of primary schools with a questionnaire asking drug-related symptoms within 2h of ingestion. The total population of sixth to eight grade school children was 210,000, and a sample size of 9096 was deemed to be representative of Ankara [(p)=1.0%, <0.05, =0.8, (d)=0.2.] During the second phase, a detailed clinical history was obtained by phone from the parents of children who had positive parent-reported drug allergy. The final stage of the study consisted of a detailed diagnostic work-up of children with a clinical history consistent with immediate type drug hypersensitivity reaction. Results Overall, 11,233 questionnaires were distributed, 10,096 of which were retrieved after completion by parents. The rate of parent-reported immediate type drug hypersensitivity was 7.87% (792 children). However, phone survey revealed a clinical history suggestive of drug allergy in only 117 children (1.16%). After further diagnostic work-up, the true frequency of immediate type drug hypersensitivity was 0.11%. Conclusion Our results suggest that a positive clinical history is not enough to make a diagnosis of drug allergy, which highlights the significance of undertaking further diagnostic evaluation.