Aromatic antiepileptic drugs, phenytoin, phenobarbital, carbamazepine and primidone, are a frequent cause of severe cutaneous adverse reactions. A strong genetic association between HLA-B*1502 and phenytoin-induced Stevens-Johnson syndrome and toxic epidermal necrolysis has been shown in Han Chinese patients.

Children whose mothers receive phenytoin during pregnancy are born with fetal hydantoin syndrome. The main features of this syndrome are mental and growth retardation, unusual facies, digital and nail hypoplasia, and coarse scalp hair. Occasionally neonatal acne will be present.