Erythromycin is used to treat infections of some bacteria that are sensitive to erythromycin and belongs to the macrolide class of antibiotics, which are generally bacteriostatic and have a bactericidal effect at high concentrations. The bacteria it treats are infections caused by Streptococcus haemolyticus and Streptococcus pneumoniae. Streptococcus haemolyticus can cause scarlet fever or purulent tonsillitis, and if the patient is allergic to penicillin at this time, erythromycin can be chosen for treatment. In addition, erythromycin can also be chosen for cellulitis, for infections caused by diphtheria bacilli and pertussis bacilli, and for infections caused by mycoplasma infections, chlamydia infections, and Neisseria gonorrhoeae. There is a risk of gastrointestinal discomfort such as nausea and some people may experience mild abdominal pain when using it.