Medication allergies are potentially important but usually poorly documented in patient medical records. Allergy awareness by clinical staff may be low in the haemodialysis population despite their regular attendance for treatment sessions. A cross-sectional study of 25 patients in a satellite unit was performed. All known allergies were not documented in 36% of patients despite the patients being known to the renal service for more than five years. 81% of allergies were medication allergies. The rest were due to topical agents. 57% (affecting 8 patients) of the medication allergies related to antibiotics (especially penicillin). Four patients had multiple antibiotic allergies. The nature and severity of these allergies was not well documented. This study demonstrates that despite being under long-term care there remains incomplete information, which is vital for optimal safe practice. Without such information, the potential for adverse events and anaphylaxis is significant in a population that is exposed to numerous pharmaceutical agents and are frequently prescribed antibiotics. Medication histories should be comprehensively re-evaluated regularly and prescribing should not occur unless the allergy box is completed.