What causes a dog to lose it’s hearing? A lot of the same things that cause hearing loss in humans. Genetic defects can cause a dog to be born deaf, this is known as congenital deafness A dog can also lose it’s hearing due to an ear infection, injury to the ear, or may experience gradual hearing loss due to old age. Exposure to loud noise can cause temporary or permanent hearing loss, as can certain drugs.
The most common cause of congenital deafness is pigment related. (There is some talk about a recessive gene as well, but nothing definite). Some dogs have white coats, but still have pigmented skin (Samoyeds, West Highland Terriers, and White German Shepherds fall into this category). Although they have white fur, they have black noses and eye rims (their fur is actually not pure white, but a very light buff color). Other dogs normally havecolored coats, and white trim (this includes Dalmatians, the white is actually not their real coat color, the “spots” are). The “trim” comes from areas of un-pigmented(pink) skin, which produces white hair. If there is un-pigmented skin in the inner ear, the nerve endings atrophy and die off in the first few weeks of the puppy’s life, resulting in deafness. Please note that you cannot tell the color of hairs in the inner ear by looking at the visible color of the dog’s ears. Although many dogs with white ears will be deaf, many deaf dogs have colored ears as well.
Hearing loss affecting both ears equally is called Bilateral Deafness. A bilaterally deaf dog is completely deaf, or deaf in both ears. Hearing loss occurring on, or affecting only one ear, is called Unilateral Deafness. A unilaterally deaf dog is partially deaf (deaf in only one ear) and has some degree of hearing in the other ear.
The above information is from www.spca.org