Severe cutaneous adverse drug reactions (SCARs) are rare but deadly drug reactions with severe damages to patients. One of the most well-known SCARs risk factors is the human leukocyte antigen (HLA) genes polymorphism. Among the HLA polymorphic alleles, the HLA-A33:03 allele has been found in association with SCARs induced by various drugs, especially in Asian people. There has not been any report on the specific detection protocol of the HLA-A33:03 allele.