Some degree of drooling is normal in dogs, particularly in breeds with loose, pendulous lips. Excessive drooling is called hypersalivation. Hypersalivation is commonly triggered by psychological events such as fear, apprehension, and nervous anxiety, as well as anticipation of food treats.
Drooling also occurs in response to mouth pain caused by periodontal disease, abscessed teeth, and stomatitis. A dog who drools excessively and acts irrationally should be suspected of having rabies. Distemper, pseudorabies, and heat stroke are other diseases associated with drooling. Another common cause of drooling is motion sickness.
Tranquilizers cause drooling, as do many poisons. When a dog drools for no apparent reason and appears healthy, look for a foreign body in the mouth.
Treatment: This depends on the cause of the drooling.