The purpose of this study was to determine and quantify the types of allergies that occur in patients with cancer. The study sample consisted of computer-generated pharmacy records of 4510 inpatients from two oncology inpatient units over a 1-year period from a large urban hospital in the USA. Compliance with computer entry was monitored in order to ensure data accuracy. Results of the study indicate that the percentages of stated allergies for persons with cancer might be higher than those for overall populations. The top four medication allergies were penicillin, sulpha, codeine and contrast media. The top four food allergies were milk, eggs, chocolate and strawberries and the top four environmental allergies were bee stings, chemical sprays, dust and mould.