Their cat drools when happy. Is this normal? Maybe not

A cat is shown at Miami-Dade Animal Services in this 2011 file photo.
A cat is shown at Miami-Dade Animal Services in this 2011 file photo. Miami Herald Staff

This column originally appeared March 12, 2017:

Q: I have an easy question: Why does my cat always drool when he's really happy?

A: Cats will produce copious quantities of saliva for all kinds of reasons. Let's consider the drooling that happens in sick cats, first:

▪ Nausea is a common cause of excessive salivation, which can happen when cats have ingested toxins or suffer from liver or kidney disease, for example.

▪ Oral pain causes drooling should they have bad teeth, electrical burns, ulcers on their gums or tongues, or injuries as a result of trauma, among other oral issues.

▪ Difficulty swallowing can cause salivation in cats.

Then there's the kind of drooling that happens when cats receive (or expect to receive) a foul-tasting or toxic food, poison or medication. Excessive salivation can ensue in these cases, too. Their brains are effectively warning their bellies that bad stuff is on its way.

The final reason for unhappy drooling happens when cats are stressed. For example, some cats will drool only when they go to the groomer or after a stressful event like being chased by a dog. Nausea often accompanies severe stress in humans, too. The difference is that cats tend to drool when they're nauseous while humans keep any excessive salivation well contained.

These reasons for drooling make sense. But what's the deal with otherwise-healthy cats who drool only when they're happy? A small but significant percentage of cats will drool when they receive positive and pleasurable stimulation. These cats will typically purr, roll over submissively and rub their saliva-smeared faces against their object of adoration (usually the invariably disgusted human pleasure provider).

Most of these inexplicably drooly cats will be lifelong "happy droolers," thereby helping distinguish them from cats who drool when sick or stressed.

Although the biological rationale for this physiologic response to positive stimulus remains a mystery, the key is to differentiate "happy cat" drooling from any sign of disease that may be causing the salivation.

Next time you see your veterinarian consider raising the issue.

Dr. Patty Khuly has a veterinary practice at Sunset Animal Clinic in South Miami. Her website is Send questions to