The redness of the glans after smearing erythromycin may be due to drug allergy, incorrect medication and other factors. 1. drug allergy: erythromycin is an antibiotic drug, mainly for bacterial infection caused by inflammation of the glans, some people may be allergic to erythromycin this drug, there will be some allergic reactions, such as redness, etc., you should stop using the drug immediately. 2. Incorrect medication: redness of the glans may may be glansitis, glansitis is divided into many kinds, may be caused by bacterial infection, may be caused by fungal infection, such as Candida albicans and so on. If it is caused by fungal infection, the use of erythromycin does not have much effect, so the glans remains redder, it is recommended to use the correct medication under the guidance of the doctor. Suffering from glans should follow the doctor’s instructions to correctly use the medication, can not blindly use their own medication, after the use of drugs appeared abnormal, should be timely communication with the doctor.