A phone call suddenly sounds muffled in one ear. Your own voice may feel oddly loud, a high-pitched ringing can appear without warning, or you may wake up feeling as though one ear has been switched off. If you are asking what causes sudden hearing loss, the most important message is this: a rapid, unexplained change in hearing needs urgent medical assessment, particularly when it affects one ear.
Not every sudden change is permanent or caused by a serious condition. Earwax, congestion and middle-ear infections can all make hearing feel blocked. However, sudden sensorineural hearing loss – a rapid loss caused by a problem in the inner ear or hearing nerve – is treated as an otological emergency. Prompt assessment gives the best opportunity to identify the cause and begin appropriate treatment.
What causes sudden hearing loss in one ear?
Sudden sensorineural hearing loss is usually defined as a noticeable hearing reduction developing over hours or up to three days. It most often occurs in one ear and may be accompanied by tinnitus, ear fullness, dizziness or imbalance. In many cases, even after detailed investigation, a single definite cause is not found.
Inner-ear inflammation or viral illness
A viral infection or inflammatory response is one possible explanation. Some people notice hearing changes during or shortly after a cold, flu-like illness or another infection. The virus itself may affect the inner ear, or the body’s immune response may cause inflammation around the delicate structures responsible for hearing and balance.
This does not mean every blocked ear after a cold is sudden sensorineural hearing loss. Eustachian tube dysfunction, where pressure cannot equalise properly behind the eardrum, is common after upper respiratory infections and can cause temporary muffling. An expert ear examination and hearing test are needed to distinguish this from an inner-ear loss.
Blood-flow changes affecting the inner ear
The cochlea, the hearing organ in the inner ear, depends on a very fine blood supply. A disruption to that supply may damage hearing quickly. High blood pressure, diabetes, high cholesterol and smoking can all affect vascular health, although sudden hearing loss can also occur in people with no known health concerns.
For this reason, clinicians consider wider medical history alongside the hearing assessment. It is not helpful to assume that stress alone has caused the problem, but sustained stress can affect sleep, blood pressure and the way symptoms such as tinnitus are experienced.
Autoimmune and inflammatory conditions
Occasionally, the immune system mistakenly attacks tissues in the inner ear. Autoimmune inner-ear disease is uncommon, but it may be considered when hearing changes fluctuate, affect both ears, or occur alongside conditions such as rheumatoid arthritis, lupus or inflammatory bowel disease.
This is one example of why a personalised assessment matters. The pattern of hearing loss, associated symptoms and medical history can point clinicians towards the most appropriate onward investigations.
Head injury, pressure change and loud noise
A blow to the head can affect the middle ear, inner ear or hearing nerve. Sudden hearing loss after a fall, sports injury or accident requires medical assessment, even if there is no obvious bleeding or pain.
Pressure-related injury can occur after diving, flying with severe congestion, forceful nose blowing or a blast of air. Loud noise exposure, including firearms, fireworks, machinery and amplified music, may also cause an immediate hearing reduction and tinnitus. The risk depends on the intensity and duration of sound, as well as whether suitable hearing protection was worn.
Medicines that can affect hearing
Some medicines are known to be potentially ototoxic, meaning they may affect hearing or balance in certain circumstances. These include particular antibiotics, chemotherapy medicines, loop diuretics and some high-dose medicines used for pain or inflammation. Risk varies substantially according to the medicine, dose, duration, kidney function and individual susceptibility.
Do not stop prescribed medication without speaking to the clinician managing it. Instead, seek urgent advice if a hearing change, tinnitus or dizziness begins after starting or changing a medicine.
Less common structural causes
Rarely, sudden or worsening one-sided hearing loss can be linked to a growth affecting the hearing and balance nerve, such as a vestibular schwannoma. These growths are usually non-cancerous and typically cause gradual symptoms, but imaging may be recommended where the hearing test pattern or clinical history warrants it.
Other uncommon causes include inner-ear disorders, neurological conditions and infections that require specialist treatment. The fact that these causes are uncommon should be reassuring, but it is also why self-diagnosis is unreliable.
Is it sudden hearing loss or a blocked ear?
A blocked sensation is not a diagnosis. Wax build-up, fluid behind the eardrum, infection and pressure problems can all reduce sound reaching the inner ear. These are described as conductive causes of hearing loss and may be treatable with targeted ear care, such as microsuction for wax when clinically appropriate.
Sudden sensorineural hearing loss can feel very similar at first. People may assume that the ear simply needs to pop or that wax is responsible, particularly when there is no pain. Waiting for it to clear, using cotton buds or repeatedly trying to force pressure equalisation can delay the assessment that matters most.
A qualified audiologist or ear clinician can inspect the ear canal and eardrum, test hearing across frequencies and identify whether the loss appears conductive or sensorineural. This distinction guides what needs to happen next.
When should you seek urgent help?
Seek urgent same-day medical advice for a sudden, unexplained reduction in hearing, especially in one ear. This is particularly important if it developed within the last 72 hours, but assessment remains worthwhile even if more time has passed.
Emergency help is needed if hearing loss occurs with facial weakness, difficulty speaking, weakness or numbness in an arm or leg, a severe new headache, confusion, double vision, collapse, or severe persistent vertigo. These can be signs of a neurological emergency and should not be managed as a routine ear problem.
Also seek prompt care after head trauma, a blast injury, severe ear pain, discharge, or sudden hearing loss with significant dizziness. Children who appear not to hear, stop responding to familiar sounds or show a marked change after illness should be assessed promptly too.
What happens at a specialist hearing assessment?
A thorough assessment begins with the story of the change: when it began, whether it was immediate or progressive, which ear is affected, and whether tinnitus, dizziness, pain, pressure or neurological symptoms are present. Your clinician will also ask about recent illness, noise exposure, injury, medication and relevant health conditions.
The ear is examined carefully to check for wax, infection, fluid, eardrum changes or injury. A comprehensive hearing test measures hearing thresholds and helps establish the type, degree and pattern of loss. Further tests may assess middle-ear function, speech clarity or the balance system where relevant.
If sudden sensorineural hearing loss is suspected, urgent medical or ENT referral is generally required. Treatment may include corticosteroids, either as tablets or delivered into the middle ear by an ENT specialist, depending on the clinical situation and suitability for the individual. These treatments are most time-sensitive early on, which is why prompt action is emphasised. Some people also require blood tests, an MRI scan or follow-up hearing assessments.
Recovery is variable. Some people regain much or all of their hearing, while others have a lasting reduction or ongoing tinnitus. Follow-up care can include hearing rehabilitation, tinnitus therapy, hearing aids where appropriate and practical support for communication at work, home and school.
Protecting your hearing while you wait for assessment
Avoid loud environments and do not insert cotton buds, ear candles or other objects into the ear. Do not use leftover ear drops unless a clinician has advised that they are suitable. Make a note of exactly when symptoms started, any new medicines, recent illnesses or noise exposure, and whether you have tinnitus or balance symptoms. This information can help the clinician act quickly.
If the problem turns out to be wax or a middle-ear issue, that is welcome news and can usually be managed appropriately. If it is sudden sensorineural hearing loss, early expert assessment is the safer choice. At Tragus-The Ear Specialists, qualified audiologists can assess sudden hearing changes and guide you towards the right next step, so you do not have to wait in silence.