What Causes A Rash When On Z Pac And Keflex?

My husband took Z pac and Keflex on Tuesday of last week. He started breaking out with a rash,I gave him some childrens Benadryl, then was very lethargic, The ambulance arrived the same time that he coded, so they put an IO in his leg, started CPR, and went to Hospital, he was then Lifelighted to an Evansville, IN hospital and put in ICU, they put him in a paralyzed state after a few hours, iced his body down to 95 degrees, then brought him out of it and had to put him back under because of blood pressure spiking, the next day they took the vent out and he started talking. He has some memory issues, is going to have some rehab, and I noticed his butt was all red and looked miserable and hurts. They gave me butt paste for it. He came home today, but when he tries to sleep, his body is jerking, he is yelling out and he is extremely fidgety. He probably has slept over 10-12 hours since Friday, the 26th of Feb. when they removed the vent. I want to know how to be sure that this is not the Stephens Johnson Syndrone.