CD4 and toxic epidermal necrolysis: Individuals taking nevirapine have a 6%–10% risk of developing a hypersensitivity reaction (HSR).1,2 This can manifest clinically as hypersensitivity syndrome (HSS) (fever, skin rash), severe blistering skin rashes, such as Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN),3 and hepatotoxicity.4 The risk of nevirapine HSR is significantly higher in individuals who start nevirapine at higher CD4+ cell counts (>400 cells/mm3 and >250 cells/mm3 for men and women, respectively).5