Generally speaking, if a four-month-old child has a white tongue, the reason may be due to milk eating and indigestion, as follows: 1. Normal milk eating leads to, if the child eats breast milk or infant formula, after drinking milk will lead to milk flaps remaining on top of the tongue, thus causing a white tongue. This is a normal physiological phenomenon, except for the white tongue, other than the mental state, milk eating condition, urination and defecation are good. For this situation, parents do not need to deal with; 2, indigestion caused by, if the tongue is white and very thick, belong to the white thick tongue moss. This is often caused by functional indigestion, in this case, children often accompanied by bad breath, and even undigested milk flaps in the stool, etc.. For this condition, you can promptly take anti-food and stagnation medicines, such as the application of Wang’s Bao Chi Wan.