Clarithromycin is one of the antibiotics in the quadruple therapy for the eradication of H. pylori, and the dosage is 0.5g/dose, twice a day, orally after meals. The choice of another antibiotic in the quadruple therapy depends on the patient’s condition, if he is not allergic to penicillin, he can choose amoxicillin, if he is allergic to penicillin he can choose other classes of antibiotics. The other two drugs are PPI and bismuth. The latest guidelines have extended the course of treatment for H. pylori from 7 days to 14 days. For the treatment of H. pylori, the history of drug allergy varies in different people and the medication needs to be decided by specific doctors.