"Blue nose pitbull" refers to pitbulls with grayish noses rather than black. These dogs are no more rare or more valuable than other pitbulls, nor are they a distinct breed. Blue nose pitbulls often have matching blue coats as well due to a recessive gene that causes the dusky gray color.
The distinct gray shade is thought to result from a recessive gene that dilutes the amount of melanin, in this case eumelanin or black pigmentation, produced. The fur and skin become lighter and look gray instead of black, ranging from a light silvery gray to a dark charcoal.
Breeding for color and appearances instead of health and temperament is strongly discouraged in the dog breeding communities. Blue and blue nosed pitbulls are bred out of a limited number of dogs, increasing the likelihood of genetic diseases and inbreeding among less ethical breeders.
Blue pitbulls are more likely to inherit skin diseases, such as alopecia and hot spots, or suffer from mange. Some breeders warn that blue and blue nose pitbulls are more likely to contract bacterial, viral and fungal infections. The Encyclopedia of the American Pit Bull Terrier has concluded that the neurological and immune systems interact in unknown ways with the cells responsible for pigmentation.