Drugs or poisons

Irritation associated with inflammation of the mouth or tongue, foreign objects in the mouth, tumors, injuries, or other defects of the mouth

Infectious diseases (such as rabies), the nervous form of distemper, or other convulsive disorders

Motion sickness, fear, nervousness, or excitement

Reluctance to swallow from irritation of the esophagus, stomach, or intestines

Injury, tumor, or foreign material under the tongue

Inflamed tonsils (tonsillitis)

Administration of medicine

Conformational defects of the mouth (eg, heavy, hanging lips)

Metabolic disorders (such as hepatic encephalopathy or kidney failure)

Abscess or other blockage or disorder of the salivary glands