Allopurinol is the most commonly used drug for the treatment of hyperuricemia 
and gout. However, allopurinol is also one of the most common causes of severe 
cutaneous adverse reactions (SCARs), which include drug hypersensitivity 
syndrome, Stevens–Johnson syndrome, and toxic epidermal necrolysis. A variant 
allele of the human leukocyte antigen (HLA)-B, HLA-B*58:01, associates strongly 
with allopurinolinduced SCAR. We have summarized the evidence from the published 
literature and developed peer-reviewed guidelines for allopurinol use based on 
HLA-B genotype.