Clarithromycin is a semisynthetic 14-membered ring macrolide antibiotic used to treat a wide range of mild to moderate bacterial infections (e.g., pharyngitis, tonsillitis, respiratory tract infections, and uncomplicated skin infections).
If you have gone through life avoiding certain antibiotics because you think you're allergic to penicillin, you'd probably want to know if you're not actually allergic.