Chow chows are well-known for having distinctive blue tongues, although it's not known why this trait occurs. Only one other breed of dog has an entirely blue tongue -- the Shar-Pei. However, many other breeds can have spots or patches of blue on their tongues.
Although usually referred to as blue in color, dark tongues on dogs can sometimes appear more like dark purple or black. It's unknown why Shar-Peis and chow chows have completely black tongues, but it's caused by extra dark pigment in the skin. In dogs who just have spots or patches of blue on their tongues, it could be likened to a birthmark on a human. In fact, dogs often have small patches of dark pigment on their skin -- you just can't see them through their coats.
Chow chows are an ancient breed, possibly one of the oldest in the world. They're known for their thick fur and cuddly, bearlike appearance, as well as for their blue tongues. Originating from China, they were kept in the Emperor's imperial kennels. Chinese legend states that they got their blue tongues at the point of creation, when one chow chow licked drops of blue from the sky as it was being painted. Although often independent and aloof, they're fiercely loyal to their families and can be very protective.
Shar-Peis are striking and distinctive dogs. Covered in wrinkled skin as puppies, they gradually lose some of their creases and folds with age. They're known to be intelligent, brave, loyal and playful. Although they form close bonds with their families, they're generally friendly and good-natured around strangers. It's thought that their blue tongues occurred as a result of some chow chow lineage in the creation of this breed.
While no breed of dog other than the chow chow and the Shar-Pei have fully blue tongues, many breeds and mixed-breeds are known to have some blue pigmentation on them, just a couple of spots or significantly larger patches. Breeds that may have some blue on their tongues include Akitas, Dobermans, Australian shepherds, Irish setters, mastiffs, Pomeranians, Dalmatians, Airedales, golden retrievers and Newfoundlands.
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