Why Do Dogs Have Cold, Wet Noses?

According to legend, God bestowed cold, wet noses on dogs for saving Noah's Ark from sinking. As the story goes, a dog was on patrol when he discovered water pouring through a hole in the hull. The quick-witted dog stuck his nose in the small hole to keep water from flooding in.

The second dog ran off to alert Noah, who quickly repaired the hole. The dogs saved the day. For their actions, God made a cold, wet nose the symbol of good health for a dog.

However, while this is often true, it is not the best barometer for health and should not be relied on. Although most people say a healthy nose should be "cold and wet," it is actually more appropriate to describe it as moist. A wet, runny nose is a sign of trouble and should be checked out by a veterinarian. By the way, a normal moist nose does not always mean a dog is healthy; if your dog has a moist nose but seems lethargic, or in discomfort or pain, consult your vet.

Conversely, a dry nose does not always signal illness. Dogs just waking from sleep often have a warm, relatively dry nose. And, some dogs, like bulldogs, just have dry noses that even chap and crack.

Despite what many people think, you cannot determine your dog's temperature by feeling his nose. A warm nose does not mean your dog has a fever. Only a properly used thermometer can tell you that. So remember, if your dog shows discomfort, lethargy or loss of appetite, you'll need to have your local vet examine him, regardless of the condition of his nose.

Dog's Sense of Smell

Imagine if each detail of our visual world were matched by a corresponding smell.

What would that be like?


Say for instance, each petal on a rose may be distinct, having been visited by insects leaving pollen footprints from faraway flowers. What is to us just a single stem actually holds a record of who held it, and when. A burst of chemicals marks where a leaf was torn. The flesh of the petals, plump with moisture compared to that of the leaf, holds a different odor besides. The fold of a leaf has a smell; so does a dewdrop on a thorn. And time is in those details; while we can see one of the petals drying and browning, the dog can smell this process of decay and aging. Imagine smelling every minute visual detail. That might be the experience of a rose to a dog.

The nose is also the fastest route by which information can get to the brain. While visual or auditory data goes through an intermediate staging ground on the way to the cortex, the highest level of processing, the receptors in the nose connect directly to nerves in specialized olfactory "bulbs" (so shaped). The olfactory bulbs of the dog brain make up about and eighth of its mass: proportionally greater than the size of our central visual processing center, the occipital lobes, in our brains. But dogs' specially keen sense of smell may also be due to an additional way they perceive odors: through the vomeronasal organ.

The vomeronasal organ, first discovered in reptiles, is a specialized sac above the mouth or in the nose covered with more receptor sites for molecules. The dog's vomeronasal organ sits above the roof (hard palate) of the mouth, along the floor of the nose (nasal septum). Unlike in other animals, the receptor sites are covered in cilia, tiny hairs encouraging molecules along. The vomeronasal organ is probably why a dog's nose is wet.

A hearty sniff not only brings molecules into the dog's nasal cavity; little molecular bits also stick onto the moist exterior tissue of the nose. Once there, they can dissolve and travel to the vomeronasal organ through interior ducts. In this way, dogs double their methods of smelling the world.

Excerpt from chapter four, Inside a Dog by Alexandra Horowitz.

The Sniff

The dog nose, in most breeds, is anything but subtle.

Dogs do not act on the world by handling objects or by eyeballing them, as people might, or by pointing and asking others to act on the object; instead they bravely stride right up to a new, unknown object, stretch their magnificent snouts within millimeters of it, and take a nice deep sniff.

As we see the world, the dog smells it. The dog's universe is a stratum of complex odors. The world of scents is at least as rich as the world of sight.

Few have looked closely at exactly what happens in a sniff. But recently some researchers have used a specialized photographic method that shows air flow in order to detect when, and how, dogs are sniffing.

The sniff begins with muscles in the nostrils straining to draw a current of air into them - this allows a large amount of any air-based odorant to enter the nose. At the same time, the air already in the nose has to be displaced. Again, the nostrils quiver slightly to push the present air deeper into the nose, or off through slits in the side of the nose and backward, out the nose and out of the way. In this way inhaled odors do not need to jostle with the air already in the nose for access to the lining of the nose. The photography also reveals that the slight wind generated by the exhale in fact helps to pull more of the new scent in, by creating a current of air over it.

Dogs naturally create tiny wind currents in exhalations that hurry the inhalations in. So for dogs, the sniff includes an exhaled component that helps the sniffer smell. Watch for a small put of dust rising up from the ground next time your dog investigates with his nose.

Warm or Cold Nose Myth

True or False: Dogs are sick when their noses are warm.



False; this is a common held myth.

The temperature of a dogs nose does not indicate health or illness. It also does not indicate if they have a fever. There is an "old wives tale" that cold wet noses indicate good health and that warm or dry noses indicate a fever or illness. The only accurate method to access a dog's temperature is to take it with a thermometer. Normal dog temperature is 100.5 to 102.5 degrees F.