In patients with the HLA-B*1502 allele, antiepileptic drugs with an aromatic ring in their structure, i.e., carbamazepine, oxcarbazepine, lamotrigine and phenytoin, have been shown to cause Stevens–Johnson syndrome (SJS) or toxic epidermal necrolysis (Lyell’s syndrome, LS). This evidence concerns the gene HLA-B and toxic epidermal necrolysis.