I glanced across the room to where the sounds of "Ich! Yuckky! His nose is all wet and cold!" were coming. These expressions of distaste were coming from Jeremy, the son of one of our neighbors. He was sitting on our sofa and was in the process of pushing away my dog Ranger, who had been nuzzling his ear.
Jeremy's mother, Colleen, leaned over to her seven-year-old son and said "A wet nose just means that the dog is healthy," she turned to me and asked, "Isn't that true?"
The myth that associates the belief that a dog with a wet nose is healthy while one with a dry nose is not has been around for ages. The best guess for how this got started comes from a time when the deadly virus associated with canine distemper was common in dog populations. One symptom of advanced distemper is hyperkeratosis, which is a thickening of the skin on the nose and the footpads. In the era when distemper was more widespread, a cool, wet nose, was considered to be a good sign that the dog did not have distemper. However, nowadays vaccination has made distemper a fairly rare occurrence in our pet dogs.
Science explains quite a bit about why dogs typically have cold wet noses. Contrary to popular belief, the nose of a dog does not sweat or produce moisture from its pores. The nose only becomes, and remains, wet because the dogs lick their noses. This moistens it with saliva and also helps to distribute mucus across the nose which helps to retain moisture levels. Because your dog's nose needs to be licked to be wet, a dog that has been asleep for a while will often wake up with a dry nose.
Your dog is licking his nose because it actually improves his abilities to smell things. For the most part, scents are carried on particles that float in the air. Having a wet nose helps to capture these small scent particles in much the same way that a wet cloth picks up dust better than a dry one. Having the scent particles clinging close to the nostrils enhances the ability of the dog to detect the smells, which probably explains the fact that the dogs that have the acutest senses of smell (such as the bloodhound) will rarely be found with a dry nose.
An extra advantage of having the scent particles clinging to the moist surface of the nose is the fact that when the dog licks the nose again to renew the level of moisture, some of the scent information from the particles on the nose will be transferred into the mouth. Once in the mouth, these odors can then be interpreted by an additional scent gland, called Jacobson's Organ, which is located on the roof of the mouth.
There is a second important reason why dogs tend to have wet noses. As you may have heard, in hot weather dogs do not keep cool by sweating in the same way that humans do (click here for more about that). Sweat helps to cool an individual because when water evaporates the place that it left gets colder. You can demonstrate this. Simply lick the end of one of your fingers and then wave your hand in the air and you'll notice that the wet fingertip feels cool as the water evaporates. Because dogs only have sweat glands on the pads of their feet, when the temperature goes up they begin to pant, and the water evaporating from their tongue and mouth helps to cool them.
If the dog's nose is wet, then evaporation of the moisture on its surface will make that area of the body cooler as well. This is useful because the dog's nose is free of fur and consists of a reasonable amount of surface area that is densely filled with blood vessels and capillaries. So cooling the nose means that this also lowers the temperature of the blood circulating through it as well, and thus it has the effect of cooling the whole body down. So a dog licking its nose now and then during the hotter days of summer might be compared to a person using a water spray on themselves to help cool down when it is really hot.
Somehow, I didn't think that all of this scientific information was going to make much of an impression on a seven-year-old so, instead, I told him the story that I had been told when I was about his age. I explained to him that when Noah had collected all of the animals in his ark to save them from the flood that God had told him was coming, he needed some help in order to make sure that things ran smoothly inside of that big crowded boat. So he gave the dogs the job of keeping watch for any trouble. One day, the two dogs were patrolling the ark and they noticed that it had sprung a leak. The hole was only about the size of a quarter, but the water was just pouring in. One of the dogs quickly ran for help. Meanwhile, the other dog did a truly brave and clever thing. He marched up to the leak and stuck his nose into the hole to stop the water from flowing in. By the time Noah and his sons arrived to repair the leak, the poor dog was in great pain and gasping for breath. However, the dog's brave deed had saved the ark from sinking. The story goes that God gave the dog his cold wet nose as a badge of honor, to remind the world of his brave deed.
Jeremy smiled and said "That's a good reason. It's nice that dogs are brave, but they should keep their noses out of my ear!"
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