More than 40 days of baby drooling may be physiological phenomenon, mouth ulcers, respiratory tract infections and so on. 1. physiological phenomenon: infant baby salivary glands will have a small amount of saliva outflow, and the baby’s swallowing function is not well developed, saliva can not be swallowed in time, so drooling more. 2. Mouth ulcers: if the baby has mouth ulcers, due to local pain stimulation will also cause the salivary glands to increase secretion, drooling more, mostly accompanied by refusal to breastfeed, crying. 3. respiratory tract infection: respiratory tract infection secretions increase, swallowing is not timely will also flow from the mouth, part of the spit bubble situation. More than 40 days of baby drooling, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.