Clarithromycin
"I am allergic to penicillin (break out in a rash) and amoxicillin (go into anaphylactic shock) so my doctor prescribed me this for a bad bout of tonsillitis. Within the first two pills (500mg twice a day) the swelling has gone down, and although the pain is still there I feel these pills are really working well for me. As for side effects I have had exactly zero. I take them with food and so far everything seems to be working well. 



It might be worth noting that during this bout of tonsillitis I have suffered severe insomnia, fever and hallucinations so even if the antibiotics did cause side effects I would not know! Brilliant drug."