In our subgroup analysis, the co‐occurrence of the TPSAB1 variant rs765144578 and the HLA‐DRB5 variant rs192498095 was strongly associated with cefaclor‐induced anaphylaxis (Table 5; OR = 657.38), suggesting a combined contribution of pathways involving IgE sensitization and tryptase‐mediated mast cell activation to the pathogenesis of this condition. This evidence concerns the gene IGHE and anaphylaxis.