The most common drug causes include Sulfa drugs (eg, sulfasalazine) Other antibiotics (eg, aminopenicillins [usually ampicillin or amoxicillin], fluoroquinolones, cephalosporins) Antiseizure drugs (eg, phenytoin, carbamazepine, phenobarbital, valproic acid and its derivatives, lamotrigine) Nonsteroidal anti-inflammatory drugs (eg, piroxicam, meloxicam) Antiretroviral drugs (eg, nevirapine) Miscellaneous individual drugs (eg, allopurinol, chlormezanone) Cases that are not caused by drugs are attributed to Infection (mostly with Mycoplasma pneumoniae) Vaccination Graft-vs-host disease Rarely, a cause cannot be identified.