Clinical studies have demonstrated association between some HLA genotypes and drug induced adverse skin reactions. Presence of HLA B*15:02 allele increases the risk of developing Toxic Epidermal Necrolysis (TEN) or Stevens- Johnson Syndrome (SJS) which is a milder form of TEN. The frequency of this allele is 10-15% in Chinese, 2-4% in South East Asians including Indians and <1% in Japanese & Koreans. This allele has also been associated with adverse reactions to Lamotrigene used for treating Epilepsy and Bipolar disorder.