Allergic responses to prescription drugs are largely preventable, and incur significant cost to the community both financially and in terms of healthcare outcomes. The capacity to minimise the effects of repeated events rests predominantly with the reliability of allergy documentation in medical records and computerised physician order entry systems (CPOES) with decision support such as allergy alerts. This paper presents an overview of the nature and extent of adverse drug reactions (ADRs) in Australia and other developed countries, a discussion and evaluation of strategies which have been devised to address this issue, and a commentary on the role of coded data in informing this patient safety issue. It is not concerned with pharmacovigilance systems that monitor ADRs on a global scale. There are conflicting reports regarding the efficacy of these strategies. Although in many cases allergy alerts are effective, lack of sensitivity and contextual relevance can often induce doctors to override alerts. Human factors such as user fatigue and inadequate adverse drug event reporting, including ADRs, are commonplace. The quality of and response to allergy documentation can be enhanced by the participation of nurses and pharmacists, particularly in medication reconciliation. The International Classification of Diseases (ICD) coding of drug allergies potentially yields valuable evidence, but the quality of local and national level coded data is hampered by under-documenting and under-coding.