Penicillin allergy, erythromycin can be used. Penicillin and erythromycin have similar antibacterial spectrums and can both be used to treat gram-positive cocci, such as Streptococcus pyogenes, Streptococcus pneumoniae, gonococcus, and meningococcus. Although allergic reactions can occur with erythromycin, they are less likely to occur with erythromycin and do not require skin testing when administered intravenously. Erythromycin belongs to the macrolide class of antimicrobials. In case of allergy to penicillin, in addition to applying erythromycin, azithromycin, clarithromycin, telithromycin, etc. of this class of drugs can also be applied. In addition to treating gram-positive cocci, macrolides can also be used to treat infections such as mycoplasma, chlamydia, legionella, and toxoplasma. The main side effect of macrolides is the occurrence of gastrointestinal irritation, which can cause nausea, vomiting, abdominal pain, etc.