After taking erythromycin, the following side effects may occur: gastrointestinal reactions include diarrhea, nausea, vomiting, stomach cramps, pain in the tongue, and decreased appetite. The incidence is related to the dose. The allergic reaction manifests as drug fever, rash, eosinophilia, etc., and the incidence rate is 0.5 to 1%. Pregnant women and lactating women should be used with caution.