A 4-month-old baby who keeps drooling and eating his hands is usually caused by the eruption of milk teeth. Some babies start to erupt their milk teeth at 4 months, which will stimulate the nerve endings of the gums and cause an increase in saliva production. Since the swallowing function of 4-month-old babies is not fully developed, they cannot swallow too much saliva, which leads to the symptom of drooling. In addition, the milk teeth will go up to the gum tissue, which will cause local itching and lead to discomfort for the baby and will relieve the symptoms by eating hands. Parents need to change the baby’s drooling towel, and also use a cotton towel to wipe the baby’s drool in time, and should ensure that the baby’s hands are hygienic. Parents can also make their baby improve the bad habit of eating hands by diverting their baby’s attention. If the baby is always drooling and eating hands is not caused by the eruption of milk teeth, it may also be caused by mouth sores, that is, ulcers in the mouth. It is recommended that parents take their babies to the hospital for examination in a timely manner and treat them accordingly according to the examination results. If it is clear that it is a mouth ulcer, the baby does not have any other discomfort, the symptoms are mild and can recover on their own, you need to pay attention to the baby’s oral hygiene, you can also use vitamin C and other drugs under the guidance of the doctor, and drink warm water in moderation to promote the baby’s internal metabolism, which can help improve the symptoms.