Patients' knowledge about their drug allergies.

OBJECTIVE--To investigate the nature and accuracy of information carried by patients about their drug allergies. SUBJECTS: 2500 new adult patients. SETTING--Accident and emergency department of a tertiary referral centre. METHODS: Patients were questioned about drug allergies. Where they claimed allergies, general practitioners were contacted for corroboration. RESULTS--242 patients (9.7%) claimed 276 allergies; 32 different drugs were implicated. Penicillin was implicated most often (151 patients); 38 patients could not remember what they were allergic to; 21 described severe reactions, but four could not remember the drugs involved. Only seven patients carried evidence of their allergies. General practitioners were contacted about 240 of the drug allergies; only 114 were confirmed as described. CONCLUSIONS--Many patients who believe themselves to have drug allergies are poorly informed about them. Emergency prescribing for these patients may risk anaphylaxis. The future acceptance of "Smart cards"would reduce this risk. In the meantime, patients with drug allergies should be strongly encouraged to carry evidence of their allergies.