The goal of this non-randomized, open-label, interventional trial is to study the efficacy of treatment for Helicobacter Pylori Infection in Preschooler aged 4-6 by Meiji Yoghurt with LG21. The main question it aims to answer is:

- whether the treatment by Meiji Yoghurt LG21 is effective by stool antigen (HpSA) test

140 qualified participants will be enrolled and non-randomized into 2 groups of the same size (product study group and blank control group). Participants of the product study group will need to eat assigned Meiji Yoghurt for 12 weeks, one bottle each day, while participants of the blank control group won't receive any intervention during the study. Four visits will be made for all participants, and relevant clinical data will be captured and recorded into CTMS (Clinical Trial Management System) for statistical analysis and reporting.

Inclusion Criteria:

• Preschooler aged 4-6 years
• H. pylori positive
• Drink milk or milk beverages regularly (more than three times a week) before joining the study
• ICF signed
• Parents or guardians agree not to participate in other interventional clinical studies during this study

Exclusion Criteria:

• Has potential metabolic class or chronic disease
• Use of antibiotics within 7 days before allocation (as judged by the trial responsible physician)
• People who have been treated for eradication of Helicobacter pylori
• Pharmaceuticals, medicinal skin care products (medical external products) and health foods that may affect gastric symptoms have been commonly used since more than one month ago
• Already under digestive system treatment
• Has lactose intolerance or protein allergy
• Those whose families had plans to leave Jinhua City during the study period
• Fails to comply with the provisions of the protocol
• Those who are deemed unsuitable as subjects by the physician