when in fact they had mononucleosis. An allergic reaction may cause an amoxicillin rash. According to the Centers for Disease ...

Amoxicillin 1000mg ... Discontinue if allergic reaction or drug-induced enterocolitis syndrome occurs. Monitor closely if skin rash develops; discontinue if lesions progress.

Amoxicillin (as trihydrate ... Discontinue if allergic reaction or drug-induced enterocolitis syndrome occurs. Avoid in those with mononucleosis. Evaluate if diarrhea occurs.