Deafness in cats stems from a handful of distinct causes: genetics, ear infections, toxic medications, growths in the ear canal, and aging. The most well-known cause is the gene responsible for white coats and blue eyes, but cats of any color and age can lose their hearing. Some forms of feline deafness are present from birth, others develop gradually, and a few are reversible if caught early.
The White Cat Gene
The single most common cause of congenital deafness in cats is a gene called W (for White). This gene does three things at once: it produces a white coat, can cause blue irises, and can destroy hearing. All three effects trace back to the same problem, a shortage or complete absence of pigment-producing cells called melanocytes.
During embryonic development, melanocyte precursor cells migrate from the neural crest to the skin, the eyes, and the inner ear. In the inner ear, melanocytes play a role that has nothing to do with color. They sit in the tissue that maintains the chemical balance of the fluid inside the cochlea, specifically by pumping potassium ions into that fluid. This potassium concentration creates the electrical charge the cochlea needs to convert sound vibrations into nerve signals. Without melanocytes, the charge never builds, and the sensory hair cells that detect sound can’t function. The cochlea and a neighboring structure called the saccule degenerate, a condition known as cochleo-saccular degeneration.
Not every white cat goes deaf, because the W gene has incomplete penetrance. One proposed explanation involves the KIT signaling pathway. Melanocytes headed for hair follicles are highly sensitive to reduced KIT signaling, so even one copy of the mutation strips the coat of color. But melanocytes destined for the inner ear and iris are less sensitive, so in some cats, enough of them survive to preserve hearing and produce eye pigment. This is why a white cat with two non-blue eyes may hear perfectly well, while a white cat with two blue eyes has a much higher chance of deafness.
The statistics are striking. Studies have found that 65 to 85 percent of white cats with two blue eyes are deaf in one or both ears. For white cats with one blue eye, the rate drops to around 39 to 40 percent. White cats with no blue eyes still carry a 17 to 22 percent chance of deafness. When deafness is unilateral (one ear), it tends to occur on the same side as the blue eye.
Ear Infections
Infections are the most common acquired cause of hearing loss in cats, and the outcome depends on how deep the infection reaches. A middle ear infection (otitis media) blocks sound from reaching the inner ear mechanically, the same way plugging your ears with your fingers muffles noise. This type of conductive hearing loss is usually temporary. Once the infection clears and the body reabsorbs the debris in the middle ear, hearing typically returns within a few weeks.
An inner ear infection (otitis interna) is a different story. When bacteria or inflammation reach the cochlea itself, they can permanently damage the sensory structures that generate nerve signals. This sensorineural deafness is irreversible. Cats with inner ear infections often show signs of vestibular disease as well: a head tilt, loss of balance, rapid eye movements, or walking in circles. These symptoms reflect damage to the balance organs that share the inner ear space with the cochlea.
Chronic ear canal inflammation from repeated or untreated outer ear infections can also narrow the ear canal over time, physically blocking sound transmission.
Ototoxic Medications
Certain medications can poison the inner ear, a side effect called ototoxicity. The most notorious class is aminoglycoside antibiotics, a group that includes gentamicin, tobramycin, neomycin, kanamycin, amikacin, and streptomycin. These drugs can cause both cochlear and vestibular damage, and the hearing loss is usually irreversible. Gentamicin tends to affect both the hearing and balance systems, while amikacin targets the cochlea more selectively. The damage can occur whether the drug is given by injection or applied topically to the ears.
What makes ototoxicity especially dangerous is that it’s progressive and subtle. Hearing deteriorates gradually, and owners and even veterinarians often don’t notice until significant damage has already occurred. Cats with kidney problems face higher risk because impaired kidneys clear these drugs more slowly, allowing them to accumulate to toxic levels. One report documented deafness in cats receiving an antiparasitic drug for intestinal infection, attributed to excessive dosing compounded by kidney failure.
Chemotherapy agents, particularly cisplatin, cause almost exclusively auditory damage. The hearing loss starts at high frequencies, progresses bilaterally, and can become profound. Loop diuretics like furosemide can also affect hearing by reducing the electrical potential inside the cochlea, though this effect is mostly temporary.
Polyps and Ear Canal Growths
Inflammatory polyps are benign growths that can develop in the middle ear, ear canal, nose, or the back of the throat. They’re most common in kittens and young adult cats between 3 months and 5 years old. When a polyp grows into the ear canal or middle ear, it physically blocks sound transmission and can trigger secondary infections that compound the hearing loss.
Signs of an aural polyp go beyond just reduced hearing. Affected cats may shake their heads, have discharge from the ear, develop a head tilt, or show facial nerve paralysis on the affected side. Some cats develop Horner syndrome, a cluster of eye-related signs including a constricted pupil, a drooping upper eyelid, and a sunken appearance to the eye on the affected side. Polyps are treatable with surgical removal, and hearing often improves once the obstruction is gone, provided no permanent inner ear damage occurred from prolonged infection.
Age-Related Hearing Loss
Like humans, cats can lose hearing gradually as they age, a process called presbycusis. The sensory hair cells in the cochlea wear down over a lifetime and don’t regenerate. Older cats may stop responding to sounds they once reacted to, sleep more deeply, startle when touched, or vocalize more loudly than usual. Because the decline is slow, many owners attribute the behavioral changes to normal aging or cognitive decline rather than hearing loss. There’s no treatment to reverse presbycusis, but most cats adapt well, relying more heavily on vision, vibration, and their sense of smell.
How Deafness Is Diagnosed
Casual observation at home can suggest hearing loss, but it can’t confirm it or distinguish one-sided deafness from full deafness. Cats are remarkably good at compensating with their other senses, and a cat deaf in one ear may appear to hear normally in everyday life.
The definitive test is the brainstem auditory evoked response, or BAER test. Small needle electrodes are placed just under the skin at the top of the head and in front of each ear. Clicks are played through earphones into one ear at a time, and a computer records the electrical activity generated along the auditory nerve pathway. The responses are averaged over several hundred clicks to filter out background brain activity, producing a waveform tracing. A normal ear generates a characteristic pattern of four to six peaks. A completely deaf ear produces a flat line. Partial damage shows up as missing or reduced peaks at specific points along the pathway, which can help pinpoint where in the auditory system the problem lies.
Most cats tolerate BAER testing without sedation. The test is particularly valuable for breeders screening white cats and for owners who suspect hearing loss but can’t tell which ear is affected. It reliably distinguishes unilateral from bilateral deafness, something no behavioral test at home can do.