The following possibilities should be considered for a sudden decrease in appetite in babies: 1. The mouth should be checked, if there is a long mouth ulcer, herpes pharyngitis, herpes stomatitis or inflammation of the teeth, etc., it will cause a sudden decrease in appetite and should be given the appropriate treatment treatment. 2. To consider that it may be sick, common intestinal viral or bacterial infections, causing a decrease in digestive function and absorption function leading to a decrease in appetite. 3. If there is a micronutrient deficiency, such as zinc deficiency, iron deficiency may also lead to a sudden loss of appetite. 4, some babies with weak constitution, poor nutrition, poor spleen and stomach function, may also experience a sudden loss of appetite when triggered by cold or improper diet.