Why is my dog drooling so much?

The Merck Veterinary Manual splits drooling into two kinds: a dog that makes too much saliva, and a dog that cannot swallow the normal amount. Its list of causes runs across both.

Motion sickness, fear, nervousness or excitement.
Drugs or poisons.
Irritation in the mouth: inflammation of the mouth or tongue, a foreign object, a tumor, an injury, inflamed tonsils.
Reluctance to swallow because the esophagus, stomach or intestines are irritated, which is what nausea looks like from the outside.
A thread, string or other object caught under the tongue. Merck also names porcupine quills and plant material embedded in the tongue, sometimes too deep to see.
Metabolic illness such as kidney failure, and disorders of the salivary glands themselves.

Merck adds one line that explains the vet's first question: the vet will try to rule out rabies first, because it is the most serious cause. That is why you will be asked about the rabies vaccine and about any bite or wildlife contact.

Call now if the drooling comes with

Pawing at the mouth, gagging or retching that produces nothing, or a dog that cannot close its mouth. Something may be stuck.
Chewing on a plant, a chemical, a medicine or a food from the list. The ASPCA Animal Poison Control Center is (888) 426-4435, and Petipedia has poison calculators.
A swollen belly, restlessness and retching. The emergency page has the bloat signs.

Before the visit

Look in the mouth if the dog will let you, for a string under the tongue, a stick across the roof of the mouth, a broken tooth, or a red or bleeding gum, and note when it started and whether the dog is eating. Petipedia has a page on bad breath and dental disease, which is the slow version of mouth pain.

Write the date it started and what you saw in the log on My Pet. The vet sheet prints it, and "since Tuesday" beats "recently".

Sources

Read 18 September 2026.