Scientists have found that lack of exposure to bacteria and germs in childhood is one of the main reasons for the sharp increase in diabetes cases among people under the age of five in recent years. Children living in rural areas are less likely to suffer from diseases such as allergies, asthma and eczema because they are exposed to bacteria earlier and have more opportunities to spend time with pets. 
Newborn babies, their body surface and body are sterile, but they start to eat milk, and after drinking water, bacteria take the opportunity to enter the body
 an environment that destroys bacteria too thoroughly may do harm to children's health.