Why do dog's have a wet nose?

It's commonly believed that you can tell a dog is healthy if their nose is cold and wet, but this is not necessarily true. Not only does a cold and wet nose not always indicate good health, but a warm and dry nose does not necessarily mean that your dog is unwell.
 
Why is A Dog's Nose Most Often Wet And Cold?

The precise reason for a dog's cold and wet nose is up for some debate, but here are a few proposed explanations:
  • Housekeeping: A dog's nose gets into everyone's business, not to mention their food bowl. A dog will quite often lick their nose in order to keep it clean, which in turn leaves it cool and wet.
  • Cooling off: Although dogs do have some sweat glands, they have considerably fewer than humans, and their skin is covered in fur which minimizes the amount of cooling that sweating can provide. Instead, dogs dissipate body heat through their mouths by panting, and via their wet noses through evaporation. Special mucous glands inside the dog's nostrils produce the clear, watery fluid that helps speed up the cooling process.
  • Scent detection: A dog's sense of smell is approximately one million times greater than ours. It's thought that a wet nose helps absorb the tiny water droplets that carry a scent, making the most minuscule odours easier to detect.
Why Might a Dog's Nose Become Dry?
  • A healthy dog's nose can often be warm and dry after sleep.
  • For some dogs, a dry, chapped nose is normal, especially with older dog's.
  • Dehydration or exertion may cause a warm, dry nose.
  • Lying in the sun or spending time near a heat source may result in a dry nose.
When Should I Be Concerned?

The temperature of your dog's nose is a poor indicator of overall body temperature. If your dog has a warm nose but is alert and acting normal, their probably in perfectly good health. However, there are some times when a dog's dry, warm nose could be of concern. If it is associated with any of the following signs, see your veterinarian right away:
  • Listlessness.
  • Acting painful.
  • Poor appetite.
  • Redness and/or flaking skin on or around the nose.
  • Presence of nasal discharge.
  • Cracked nose and/or sores and scabs on the nose.
Even if your dog's nose is wet and cool, any of the above signs require a visit to the veterinarian.