0Re-design 8 years ago ReplyUpvoteDogs don't really have lips like a human. Lips on a dog are made of skin tissue, and a human's lips are actually made of a different tissue. Not all dogs have black "lips". If they have black lips it's because their skin is dark under their hair. They have less hair around their mouth and it gets even darker since it's exposed to the sun and cold. A dog's skin will darken considerably if exposed to the cold.