The clinical trial will be carried out in China Medical University Hospital. The overall plan is a double-blind trial. All recruited 3 months-3 years old atopic dermatitis (AD) patients are divided into two groups, 50 in each group and 100 in two groups. The two groups are placebo and Bifidobacterium longum CCFM1029. The entire evaluation plan lasts for 3 months. The number of probiotic bacteria is 5 billion per capsule, and the number of bacteria taken by the subjects is 5 billion per day (one capsule before bed each day). During the planning period, the eczema area and severity index (EASI) score of the patient's dermatitis was evaluated every month, and the score differences of dermatitis before and after taking probiotics was observed. In addition, subjects must perform two fecal samplings before and after the trial, and the isolated DNA was analyzed using the next-generation high-throughput sequencing method (NGS) for subject fecal flora changes. Comparing the two groups before and after taking the capsule, whether the intestinal flora changed. Statistical analysis of the relationship between changes in intestinal flora and the degree of AD. Through the above test, the investigators evaluated whether Bifidobacterium longum CCFM1029 can regulate the pediatric intestinal flora and relieve the inflammatory response in the body, thereby regulating atopic dermatitis.

Inclusion Criteria:

• Subjects were between 3 months and 3 years old.
• For patients diagnosed with atopic dermatitis by a professional physician and the EASI score is greater than 5, the type and frequency of drugs used during the experiment should be recorded.
• The subject's parents agree to join the trial and sign the informed consent form.

Exclusion Criteria:

• The patient who has a history of allergic reactions, or the use of other highly sensitive or contraindicated drugs (allergy to antibiotics or antipyretics).
• The patient who has taken oral immunosuppressants and systemic steroids within the past 2 weeks.
• The patient who has consumed probiotic-related products (including drops, lozenges, capsules, powder or yogurt) within the past 1 month.
• The patient who has participated in other clinical studies within the past 1 month.
• The patient who has received immunotherapy within the past 1 year.
• The patient who suffering from major diseases (with a IC card for severe illness), congenital diseases.
• The patient who is not suitable to participate in the trial as assessed by the professional physician.