Three and a half months baby fart stinks, may be due to breast milk problems, indigestion, acute gastroenteritis and other reasons. 1. Breastmilk problem: If the mother eats food with high fat or protein content, part of the protein will enter the baby’s body through the breastmilk, and the part of the protein that the baby can’t absorb may cause the baby to fart smelly in the intestinal tract. 2. indigestion: three and a half months baby’s digestive function is not yet well developed, if eat too much breast milk, the baby can not be digested, easy to be decomposed by bacteria to produce gas, which leads to the phenomenon of fart odor. 3. acute gastroenteritis: if the baby’s abdomen is cold may cause acute gastroenteritis, inflammation may cause gastrointestinal tract dysfunction, food in the gastrointestinal tract is not timely digested will be fermented to produce hydrogen sulfide and other gases, the baby may appear to fart symptoms. Three and a half months baby fart stinks of many other reasons, need to consult a doctor in time to clarify the cause, and by the doctor standardized treatment, do not self-medication, so as not to cause adverse consequences.