The baby old tongue can be caused by physiological factors, such as salivary secretion, imitation of others, etc., but also does not exclude pathological factors such as oral diseases, Down’s syndrome, etc.. 1. Physiological factors: when the baby is two months old, the salivary glands will start to secrete saliva, the swallowing function is not perfect, saliva will flow out from the corner of the mouth, the baby unconsciously sticking out the tongue and licking, and if the parents are often in front of the baby to stick out the tongue, the baby will go to learn and imitate. 2. Pathological factors: the baby’s immunity is poor, easy to be affected by external factors, there will be ulcers or herpes in the mouth, when the mouth feels uncomfortable, the baby will also spit out the tongue. In addition, Down’s syndrome may also cause the baby old tongue, Down’s syndrome is the most common chromosomal disease, the baby has a special face, wide eye spacing, small ears, tongue fat, like to stick out of the mouth, salivation and other phenomena. The baby old tongue may also have other reasons, it is recommended to go to the hospital in time for relevant examination, clear cause of the disease after active symptomatic treatment.