This is an example of the hair I trimmed off a shitzu's face. As you can see the hair on the left is dry. But the hair on the right is wet and stained brown. The hair on the right came from the lips where the dog licks the hair inside his mouth. The hair is always in the mouth and if long enough can wrap around the teeth. Many times I have had to take a dental pick and untangle the hair from the teeth. This hair smells and causes tooth decay. Not only that can you imagine having hair in your mouth all the time and not be able to get it out? The more you lick the more you pull inside. Yuck. Next time you are watching TV with your pup on your lap lift their lip and see if you can find this happening to your dog.