Q. I read that a dry nose means a dog is sick. Is this true?

A. To really get to the bottom of this, we need to understand why a dog’s nose is wet in the first place. Tears are constantly produced to lubricate the movement of the eyes. Because this lubrication is so critical to eye health, the dog’s body routinely produces more tears than are needed. These excess tears flow through the nasolacrimal (literally “nose-tears”) duct and out the base of the nose. (People experience this when crying.)

As the tears drip down into the dog’s face, the dog licks her nose, spreading the tear fluid over the nose, which wets it. Then, evaporation causes the nose to be cool. The moistened nose is better equipped to dissolve airborne chemicals, which contributes to a better sense of smell.

No More Tears (or Wet Nose)

When a dog is sick, the body uses up more internal water in the process of fighting disease. This increased use, especially with a fever, causes relative dehydration, even if the dog is drinking a normal amount of water. This dehydration results in decreased tear production, and hence a dry nose.

The same dry nose, however, could be because of fluid loss from panting on a hot day. And some dogs (such as Poodles and Lhasa Apsos) are prone to blocked tear ducts, so there is less fluid flowing through the ducts to moisten the nose. The bottom line is that the dry nose may be an indicator of dehydration, but it indicates illness only if it’s coupled with lethargy and other symptoms.

In other words, a sick dog may have a dry, warm nose, but a dry, warm nose can also be the result of something other than illness.