Generally speaking, the causes of drooling in three-week-old babies include the following conditions. First, the symptoms caused by children suffering from stomatitis. After children are infected with viruses, bacteria and other pathogens that cause stomatitis, they will have symptoms such as herpes in the mouth, pain in the mouth as well as drooling, poor appetite for meals and even fever. For children with stomatitis, you can give them Blue Scutellaria Oral Liquid or Shuangjinlian Oral Liquid. Secondly, drooling is caused by mental retardation in children. Children with severe mental retardation may also have symptoms such as drooling and dull eyes.