A child with smelly breath should be a manifestation of bad breath in children. It should be considered caused by gastrointestinal dysfunction, which is a manifestation of poor digestive function. In terms of diet, you need to give your child some easily digestible food, avoid eating greasy, raw and cold food. During this period of time, no new complementary foods can be added, and the amount of the original complementary foods can be appropriately reduced, up to two-thirds of the original. If the child is formula-fed or breast-fed, the amount of milk needs to be reduced appropriately and the concentration of formula needs to be lowered appropriately. You can give your child some oral intestinal micro-ecological preparations to improve the intestinal micro-ecological environment, such as Bifidobacterium or Saccharomyces boulardii, Pauleon, Mamma’s Aid and other such drugs. In addition, you need to pay attention to whether the child has oral infections, such as mouth ulcers, dental caries and other causes of bad breath.