Patch testing and sensitization to multiple drugs

Summary Background Adverse drug reactions pose an increasing diagnostic challenge in hospitals and in outpatient clinics. When consecutive or repeated allergic drug eruptions are suspected, patch testing is a useful diagnostic tool for determining the causative drugs. Objectives The aim of the study was to identify patient cases with multiple delayed‐type drug sensitizations by using patch testing. Methods Eight hundred and eleven patients with suspected drug allergy were patch tested during a 9‐year period. Results Multiple delayed drug sensitizations were found in 12% of those patients with positive results in drug patch testing. Conclusions Drug patch testing is useful in cutaneous adverse drug reactions where multiple drugs are suspected. Multiple drug sensitizations can be found in a proportion of patients who have delayed drug allergies. In addition to drug reactions with eosinophilia and systemic symptoms, these patients may have repeated exanthemas or contact dermatitis.