Diarrhea in children has always been a concern for parents and friends, so we all want to know what causes diarrhea in children and what to do about it. Then today we will introduce to you the common causes of diarrhea in infants and children and how to deal with it. The causes of diarrhea can be divided into two main categories, infectious and non-infectious. Infectious refers to viruses, bacteria, fungi, parasites, etc. Non-infectious factors, such as improper diet, milk protein allergy, lactose intolerance, climatic factors, etc. Among them, protein allergy and lactose intolerance are the more common reasons for babies within 1 year old, and many parents are not clear about these two cases, so today we will focus on the difference between these two. Diarrhea is one of the most important manifestations, and some parents say that their children poop as soon as they eat milk. In addition, there can be blood in the stool, vomiting, sleeplessness, and active bowel sounds (some parents also say that their children’s stomachs grumble when they eat milk). Some children may have symptoms outside of the digestive tract, such as eczema or even asthma attacks, all of which may be related to protein allergies. The eight most common food groups that cause protein allergies are: milk, beans, wheat, peanuts, nuts, eggs, fish, shrimp and crabs. The main treatment is to avoid these foods, and if the child is exclusively breastfed, the mother should strictly avoid these foods for at least two to four weeks. If the effect of avoidance is not obvious, or if the child is mixed feeding, we should consider switching to hydrolyzed milk powder and observe for at least two weeks, if effective, to consolidate for 4-6 months. Lactose intolerance, on the other hand, is a deficiency of lactase in children due to various reasons, and the lactose in food cannot be digested and fermented in the intestine, thus causing diarrhea, bloating and other manifestations, with stools containing a lot of foam and a very distinct sour smell, which can be determined by checking stools or urine reducing sugar. The treatment of lactose intolerance is mainly to supplement lactase or use lactose-free milk powder, and the symptoms will be significantly improved. It is important to mention that milk protein allergy and lactose intolerance may coexist because protein allergy causes damage to the intestinal mucosa, which leads to a large loss of lactase at the intestinal villi and subsequently to lactose intolerance. This is something that you need to be aware of.