Deafness is the complete or partial lack of hearing. It can be hard to assess in dogs, because they can’t discuss their hearing difficulties. Deafness in one ear is especially difficult to detect. Anything that injures the ear canal, ruptures the ear drum or interferes with the tiny bones inside the ear can contribute to deafness, including infections, tumors, waxy build-up, repeated exposure to gunfire and nerve degeneration associated with old age. Some dogs are born deaf; this can be associated with whiteness of the head and ears. Normal puppies respond to sound by about 2 weeks of age. Attentive breeders recognize hearing problems well before a puppy is ready to leave for its new home. Owners may not notice deafness until their dog stops following commands or responding to familiar sounds, such as doorbells. Fortunately, most dogs adapt to relying on other senses in place of one they lose or never had.