Why do dogs have wet noses?

Have you ever felt a dog press a cold, wet nose against your hand? That little damp spot is not a sign that the dog is healthy. It is the outside of a very clever machine.

The tip of a dog's nose is called the rhinarium. It is a patch of skin with no fur on it. It stays wet in three ways: tiny glands under the skin make a thin layer of slime, tears drain down a tube from the eyes, and the dog keeps licking it.

Job one: catching smells. Smell molecules float in the air. If they bump into dry skin, most of them bounce away. But if they land on a film of water, they dissolve and stick. When the dog sniffs, those trapped molecules are carried deep into the nose, where the smelling cells live. A dry nose means a blurry world.

Job two was discovered in 2020. Scientists in Hungary and Sweden trained three dogs to choose which of two far-away objects was warm. The dogs could do it — they noticed a tiny bit of heat from about 1.5 metres away. Why? Because water evaporating makes the nose cooler than the air around it, and a cool nose feels heat better. Before this, only snakes and vampire bats were known to have this skill.

One more thing: a dry nose does not mean a sick dog, and a wet nose does not mean a healthy one. Dogs often wake up with a dry nose.

Try it yourself: sprinkle a few breadcrumbs on a table. Press them with a dry finger, then with a wet finger. The wet finger picks up more crumbs. That is exactly how a dog's nose grabs smells.