Stevens-Johnson Syndrome (SJS) is a rare life-threatening condition characterized by severe mucocutaneous epidermal necrolysis and detachment of the epidermis. The condition centers around a delayed-type hypersensitivity reaction with a complex etiology stemming from a variety of causes. The number one cause is medication-related-common ones including sulfonamides, antiepileptics, allopurinol, and nonsteroidal anti-inflammatory drugs. Genetics also play a role as several human leukocyte antigen (HLA) genotypes within certain ethnic groups have been implicated in adverse reactions to specific drugs. HLAB*15:02 has been identified in the Chinese and others of Southeast Asian origin to increase susceptibility to lamotrigine and carbamazepine-induced SJS. Furthermore, patients of Japanese origin with HLAB*31:01 and Koreans with HLA-B*44:03 are also at increased risk of SJS after receiving the same two drugs. Of the antiepileptics, one most commonly associated with SJS is lamotrigine, a pre-synaptic voltage-gated sodium channel inhibitor. Lamotrigine is an antiepileptic drug of the phenyltriazine class that is indicated for the prevention of focal and generalized seizures in epileptic patients as well as monotherapy or adjunctive maintenance treatment for Bipolar disorder. The occurrence of SJS is not a rigid contraindication to lamotrigine reintroduction in the same patient. To facilitate this, manufacturers have developed a strict re-challenge dosing regimen to facilitate successful reintroduction of lamotrigine. In order to prevent the recurrence of SJS during a re-challenge, timing of re-dose and initial rash severity must be considered. Therefore, to prevent SJS recurrence, prime lamotrigine re-challenge patients are those with mild initial rash that has not occurred within the previous 4 weeks. The Federal Food and Drug Administration recommends the testing HLA subtypes for those associated with SJS prior to starting lamotrigine.