Dogs' noses are wet for several important reasons related to their sense of smell and temperature regulation. The moisture on a dog's nose comes from mucus secreted by special glands inside the nose, as well as saliva from licking their noses. This wetness helps scent particles stick to the nose, enhancing their ability to detect smells, which is crucial since dogs rely heavily on their sense of smell to understand their environment. Additionally, a wet nose helps with cooling since dogs do not sweat like humans; moisture evaporates and aids in heat dissipation. Dogs also lick their noses to keep them clean and moist, which further supports their exceptional olfactory capabilities. In summary:

• A thin layer of mucus helps absorb scent chemicals, improving smell.
• Dogs lick their noses to keep them moist and clean, also helping to transfer scents to the Jacobsen’s organ in the roof of their mouth.
• Moisture on the nose helps with cooling through evaporative heat loss.
• Environmental factors like humidity and activity level can influence how wet a nose is.

The wetness of a dog's nose isn't a definitive sign of health or illness alone, as dryness can be normal at times, such as when the dog is sleeping.