You're sitting quietly on the couch when you feel a cold, wet nose nuzzling your face or hand. Your dog is trying to tell you something, but you don't know what it wants. All you know is that his nose feels like an Antarctic snow storm — a sign of good health — or so you've been taught. Frankly, whether a dog has a wet nose is not a signal, one way or another, of good health. It's an old wives' tale that has no basis in fact.
So, why are dogs' noses sometimes dry and sometimes wet? No one knows for sure, but there are myriad theories. One suggests that because dogs are always licking their noses, their salvia helps paint their snoz with mucus produced in the nostrils. As a result, all that mucus-licking improves a dog's ability to smell things.
How does that work? When dogs sniff the air — they are always sniffing the air — they inhale tiny suspended particles. These particles get trapped in their nasal mucus, which helps the dog figure out what they are smelling. As a dog licks his or her nose, it picks up some of the scent-laden goop. The tongue then brushes against an olfactory gland on the roof of the mouth, which helps our four-legged companions figure out what they are exactly smelling.
Another reason, some have suggested, is that a wet nose helps keep a dog cool in warm weather. When we humans sweat, the perspiration our sweat glands produce evaporates, cooling us down. Dogs, however, do not sweat. That's because they have no sweat glands, except on the bottom of their paw pads. Instead they pant to cool off.
However, a dog's nose, unlike the rest of its body, is not covered in fur. It also brims with blood vessels. When a dog licks its nose, the theory suggests, it is cooling itself down as saliva, like human sweat, evaporates. That leaves the surface area of the nose cool, along with the blood circulating in and around Fido's snout. Consequently, cooler blood flows through the dog's body, keeping our best friends a bit cooler.
Still, why are dogs noses often dry? For one thing, they might not be licking it much. Touch your dog's nose in the morning. Chances are, it'll be as dry as the Sahara. That's because as a dog sleeps, it rarely licks its nose. Certain breeds, like bulldogs and pugs, also have noses that are mostly dry. Age also tends to make a nose dry.
The bottom line is that if your dog has a dry nose, chill out. The dog isn't sick. Wait a few hours and it will be wet again.