Three and a half year old children drooling a lot may be related to bad habits, dental caries, mouth ulcers and so on. 1. Bad habits: small children because of the development of salivary glands will show a lot of saliva, can not swallow in time there will be a lot of saliva. 2. Dental caries: children’s oral hygiene is not good to produce dental caries, dental caries will repeatedly stimulate the salivary glands, resulting in the symptoms of drooling. 3. Mouth ulcers: children with mouth ulcers, pain may cause the child does not want to swallow saliva, will cause saliva. Three and a half year old children drooling a lot may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor’s treatment.