That sounds aweful. I'm still on guard about the flu and make sure I wash my hands very regularly at work (big time important in a University setting).
I had a reaction to penicillin when I had mono and strep throat years ago even though I'm not allergic to penicillin. Same thing as you, a rash all over. The doctor told me that it can cause a reaction in combination with some viruses, in my case the mono virus. So, you'll likely be able to take that antibiotic again as long as you aren't figiting off a virus at the time.