According to the British Society for Allergy and Clinical Immunology (BSACI), 6.5% of hospital admissions are caused by adverse drug reactions and contribute to prolonged hospital stay in up to 15% of cases [2]. Immediate allergic responses such as anaphylaxis are immunoglobulin E (IgE) mediated, as they are caused by IgE against a specific allergen, whereas delayed reactions are usually non-IgE mediated, as they do not involve immunoglobulin E but may be mediated by other immune mechanisms, such as T-cell response; these may include delayed skin reactions like maculopapular rashes. This evidence concerns the gene IGHE and anaphylaxis.