For dog owners, it can be hard to admit their furry companion has flaws. Sprinting through the house after a bath is one. Stealing your spot on the couch is another. And so is the habit exhibited by some breeds of drooling enough to fill an in-ground pool.

Entire movies, like 1992’s Beethoven, have been made on the perils of dog drool. So why do they do it?

In most cases, the cause of visible drool is benign. Dogs, like humans, excrete saliva in order to help facilitate the digestive process. Saliva moistens food—which may be one reason why pooches can seemingly siphon entire chunks of dry food like a Dyson—and also helps clear the mouth of bacteria to maintain oral health. If a dog begins drooling visibly, they’re probably getting excited in anticipation of their next meal. (It could be argued dogs are always anticipating their next meal, but that’s another story.)

If a dog is being particularly slobbery, it’s possible it’s a symptom of an underlying problem like digestive upset, having ingested a foreign object, or a tumor. It’s important to get a dog examined if they begin drooling excessively or if there’s blood in the saliva.

Certain breeds like the St. Bernard, Basset Hounds, or Mastiffs have a reputation for drooling puddles, but it’s not necessarily because they’re producing more of it. Instead, breeds with certain mouth configurations or uneven lips can make it difficult to contain drool, leading to leakage.

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