Babies always tongue licking chin may be physiological causes, may also be pathological causes, such as Down’s syndrome, hypothyroidism and so on. 1. Physiological reasons: Due to the baby’s age is small, and swallowing ability is poor, when the mouth saliva secretion more will flow out of the corner of the mouth, this time the baby will be through the tongue, lick the chin, etc. will be licked clean by the corner of the mouth saliva. There are also some babies due to curiosity, will habitually stick out the tongue, generally with the gradual growth of the baby’s age, this phenomenon will disappear. 2. Pathological causes: (1) Down’s syndrome: Down’s syndrome is a chromosomal disorder caused by an abnormality of chromosome 21, which can cause babies to always lick their chins with their tongues, accompanied by upward slanting of the eyes, salivation (drooling), and small outer ears and other symptoms. (2) Hypothyroidism: If a baby has hypothyroidism, he or she will often have symptoms such as tongue sticking out of the mouth, drooling, tongue licking chin, etc., which may also be accompanied by inattention, memory loss and other abnormalities. The baby always tongue licking chin exclude physiological factors, should be timely to the hospital, identify the cause of the disease, the cause of treatment.