When i reacted to penicillin, I just swelled up and went red all over. There was no rash as such. I was lucky, it was more than 40 years ago and penecillin reaction wasn't heard of much, because my glands were swollen and I felt so poo, my mother thought it was glandular fever or mumps and took me down to the doc (it was wait to be seen then, no appointments) and it was the doc who diagnosed an allergy and told me NEVER to have penecillin again as the next time could kill me.