Tejedor-Alonso MA, et al. - Researchers performed a systematic review and meta-analysis of observational studies to evaluate how beta-blockers (BBs) and angiotensin-converting enzyme inhibitors (ACEIs) impact anaphylaxis. They identified the relevant studies from PubMed/MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews, and the Web of Science. The studies analyzed were those where the presence and severity of anaphylaxis were compared between patients taking BBs, ACEIs, both types of drug, or neither type of drug. A random-effects model was used for meta-analysis. They found low quality evidence demonstrating that use of BBs and ACEI increases the severity of anaphylaxis. The low quality of evidence was attributed to differences in the control of confounders due to the concomitant presence of cardiovascular diseases.