My Yorkie Has Developed White Spots On His Nose. His Nose Was All Black Before. What Could It Be?

Dog nose can be of  liver color, black or  pink but it depends upon breed. Some changes in nose color of dog are considered as normal and some abnormal. Natural causes of change of nose color in dogs are

   1. Aging
   2. Temperature

In old age, function of an enzyme called tyrosinase is reduced that can lead to loss of pigmentation. Function of this enzyme is also temperature sensitive and is increased in hot weather and decreased in winter. This is reason of snow nose or winter nose in dogs.
Change of nose color in dogs can also be due to

1. Ttrauma
   
2. Abrasion
   
3. Contact dermatitis
   

If your dog nose has changed with no other trouble then no need to be worried. Otherwise take your dog to vet for proper diagnosis and accurate treatment.