PH
The moisture on a dog's nose has a useful sensory function. Scent molecules can adhere to moist surfaces, helping dogs process smells as they investigate their surroundings.
Dogs also regularly lick their noses, maintaining that moist surface while cleaning away particles.
A wet nose isn't therefore a reliable medical test for whether a dog is healthy or sick. The more interesting point is that moisture contributes to the remarkable smelling system dogs use to interpret their environment.
© American Kennel Club