HLA-B and toxic epidermal necrolysis: The allopurinol bula reads: (i) “HLA‐B*5801 has been identified as associated with risk of hypersensitivity and STS/TEN (Stevens‐Johnson syndrome/toxic epidermal necrolysis) caused by allopurinol”; (ii) “use of genotyping as a tool to make decisions about allopurinol treatment has not been established”; (iii) “if the patient is a known carrier of HLA‐B*58:01, use of allopurinol may be considered when benefits are superior to risks”.