I had the identical thing happen to me. I was given Amoxicillin when I was 17 and misdiagnosed with a strep infection. I actually had mono, and promply developed a rash. I tried to take amoxicillin about 5 yrs after that and again broke out. I assumed I somehow developed an allergy (but I'm not sure if this is really the mechanism). Now I'm 35 and ... more