Ilosone is used to prevent and treat infections in many different parts of the body, including respiratory tract infections, skin infections, diphtheria, intestinal amebiasis, acute pelvic inflammatory disease, Legionnaire’s disease, pertussis, and syphilis. This medicine is also used to prevent recurrent attacks of rheumatic fever in patients who have had an allergic reaction to penicillin or sulfa drugs. Erythromycin belongs to the class of medicines known as macrolide antibiotics. It works by killing bacteria or preventing their growth.