What Causes Sudden Hearing Loss In One Or Both Ears?

Sudden hearing loss is exactly what it sounds like: a rapid drop in hearing that happens all at once or over a few days. It can strike one ear or, less commonly, both ears. The most frequent cause is a viral infection that affects the inner ear, though the exact trigger often remains unknown. Other causes include head trauma, certain medications, autoimmune conditions, and circulation problems. Because prompt treatment can influence recovery, sudden hearing loss is considered a medical emergency that needs evaluation right away.

What Is Sudden Sensorineural Hearing Loss?

Doctors use the term sudden sensorineural hearing loss (SSNHL) for most cases of rapid hearing decline. Sensorineural means the problem lies in the inner ear or the nerve pathways that carry sound to the brain. This is different from conductive hearing loss, where sound waves cannot reach the inner ear because of earwax, fluid, or a damaged eardrum.

In SSNHL, the hearing loss is typically 30 decibels or more across three connected frequencies. That is roughly the difference between a quiet room and normal conversation. The loss usually appears in one ear, but about 2 to 5 percent of cases involve both ears.

Most people notice the loss when they wake up in the morning. Others hear a sudden pop followed by muffled hearing. About half of people also experience tinnitus, which is ringing or buzzing in the affected ear. Some report dizziness or a feeling of fullness in the ear.

What Causes Sudden Hearing Loss In One Or Both Ears?

In most cases, doctors cannot identify a single clear cause. This is called idiopathic sudden sensorineural hearing loss. It accounts for roughly 90 percent of cases. That does not mean there is no cause — it means current testing cannot find it.

When a cause is identified, viral infection tops the list. Herpes viruses, including the virus that causes cold sores, and other respiratory viruses can inflame the inner ear. The inflammation disrupts the delicate hair cells that convert sound vibrations into nerve signals. Without those signals, the brain receives nothing.

Other recognized causes include:

• Head injury, especially fractures of the temporal bone near the ear
• Autoimmune diseases such as lupus or rheumatoid arthritis that attack inner ear tissue
• Blood circulation problems that reduce oxygen supply to the inner ear
• Certain medications, called ototoxic drugs, that damage hearing
• Bacterial or viral infections of the inner ear, including meningitis
• Tumors on the auditory nerve, such as acoustic neuroma

Bilateral sudden hearing loss — affecting both ears at once — is rarer and more concerning. It raises suspicion for autoimmune disease, systemic infection, or a condition affecting the entire body rather than just one ear.

How Is Sudden Hearing Loss Diagnosed?

Diagnosis begins with a hearing test called audiometry. This measures the softest sounds you can hear at different pitches. The test confirms whether hearing loss is present and how severe it is. It also helps distinguish sensorineural loss from conductive loss.

Doctors may order blood tests to check for autoimmune markers, infections, or thyroid problems. Imaging with an MRI can rule out tumors or structural damage. In some cases, a referral to an ear, nose, and throat specialist — an otolaryngologist — is needed for a complete workup.

Time matters. The inner ear hair cells can die permanently if the underlying problem is not treated quickly. Delaying evaluation by weeks reduces the chance of recovery.

What Treatments Are Available?

Corticosteroids are the main treatment for sudden sensorineural hearing loss. These drugs reduce inflammation in the inner ear. They can be taken orally or injected directly into the middle ear, where the medication seeps into the inner ear. Both methods are used in clinical practice.

Treatment usually begins within two weeks of symptom onset. The earlier treatment starts, the better the odds of meaningful recovery. Some studies suggest starting steroids within the first 72 hours gives the best results, but treatment can still be offered beyond that window.

Recovery rates vary widely. About half of people regain most or all of their hearing, often without any treatment. Another portion recovers partially. For some, the hearing loss is permanent. Mild cases carry a better outlook than severe ones. People with dizziness tend to have a worse prognosis than those without it.

When a specific cause is found, treatment targets that cause. Antibiotics treat bacterial infections. Immunosuppressants may help in autoimmune cases. Surgery might be needed for tumors. But for the majority of cases without an identified cause, steroids remain the standard approach.

Can Sudden Hearing Loss Be Prevented?

Because most cases have no known trigger, there is no reliable way to prevent sudden hearing loss. Managing overall health may reduce some risk. Controlling blood pressure, avoiding ototoxic medications when possible, and protecting ears from loud noise are reasonable steps, though none of these guarantee protection.

Vaccination against certain infections, such as meningitis, reduces the risk of hearing loss from those specific diseases. But no vaccine exists for the common viruses suspected in most cases.

What matters most is recognizing the symptom and acting fast. Sudden hearing loss is not something to wait out. The difference between seeking care quickly and delaying can be the difference between recovery and permanent hearing loss.

Is Sudden Hearing Loss an Emergency?

Yes. Sudden hearing loss is treated as a medical emergency in most clinical settings. The inner ear has a limited window during which treatment is most effective. Waiting even a few days can reduce the chance of recovery.

Go to urgent care or an emergency department if you notice a sudden decrease in hearing, especially if it happens over hours or days. Do not assume it is earwax or allergies. While those can cause muffled hearing, they rarely cause true hearing loss. Only a hearing test can tell the difference.

If you also have dizziness, facial weakness, or severe headache, seek care immediately. These symptoms can indicate a more serious condition such as stroke or a tumor pressing on the nerve.

What Is the Outlook After Sudden Hearing Loss?

Prognosis depends on several factors. The severity of initial hearing loss matters. People with mild to moderate loss recover more often than those with profound loss. Younger age is associated with better recovery. The absence of dizziness is a positive sign.

About one-third of people recover completely without treatment. Another third improve partially. The final third experience permanent hearing loss. With steroid treatment, recovery rates are somewhat higher, though the evidence comparing treated and untreated groups is not as strong as doctors would like.

Even when hearing does not fully return, many people adapt well. Hearing aids, assistive listening devices, and counseling can help. Some people find that tinnitus, if present, fades over time. Others need ongoing support to manage it.

When Should You See a Doctor?

See a doctor the same day you notice sudden hearing loss. If your regular clinic is closed, go to urgent care. Do not wait for the weekend to pass or for symptoms to resolve on their own.

Bring a list of all medications you take, including over-the-counter drugs. Some medications, such as high-dose aspirin, certain antibiotics, and some chemotherapy drugs, can damage hearing. Knowing what you take helps the doctor identify a possible medication-related cause.

Be honest about any recent illnesses, injuries, or exposures. A viral respiratory infection weeks before the hearing loss is a common finding. Recent head trauma, even if it seemed minor, is also relevant. Every detail helps narrow the cause.