Hearing Loss in One Ear Only: Causes, Warning Signs and What an ENT Does

Most people don’t notice hearing loss gradually. It tends to sneak up, the television volume creeps higher over months, conversations in noisy environments become increasingly exhausting, and at some point someone else mentions it before the person acknowledges it themselves.

One-sided hearing loss where the problem is clearly worse in one ear than the other follows a similar pattern of quiet adaptation. The good ear compensates. The person instinctively turns their head to position the better ear toward whoever is speaking. They start sitting on a particular side at tables. They switch which ear they use for phone calls.

And then months pass. Sometimes years. The adaptation has become so automatic that the hearing loss is almost forgotten, until something makes it impossible to ignore. Or until an investigation for something else picks it up incidentally.

One-sided hearing loss deserves earlier attention than it usually gets. Not because it’s always serious most causes are entirely manageable but because some causes are time-sensitive, and because the longer certain conditions are left, the harder they are to treat effectively.

Why One-Sided Hearing Loss Is Different From Two-Sided

When both ears are affected equally as in age-related hearing loss or noise-induced hearing loss from years of loud music, the brain adjusts symmetrically and the person often doesn’t notice until the loss is significant. One-sided loss is different the brain is receiving two very different signals, and the asymmetry creates specific difficulties:

Localising sound – the ability to tell where a sound is coming from depends on the brain comparing the timing and volume of signals arriving at both ears. With one ear significantly worse, this ability is lost. The person can hear a sound but can’t tell where it’s coming from.

Hearing in noise – in quiet environments, the good ear often compensates well enough that the person manages. In noisy environments a restaurant, a crowded room, a party, the inability to use both ears together makes separating speech from background noise dramatically harder.

Telephone and directed conversations – conversations on the affected side become genuinely difficult rather than just slightly harder.

These difficulties are often attributed to “just being inattentive” or “not concentrating” which is why one-sided hearing loss gets dismissed or adapted around for so long.

How the Ear Works A Brief Overview

To understand the causes of one-sided hearing loss, it helps to know the basic anatomy involved.

Sound travels down the ear canal and hits the eardrum, causing it to vibrate. These vibrations are transmitted through three tiny bones the ossicles in the middle ear to the oval window, the entrance to the inner ear. In the inner ear, the cochlea converts these mechanical vibrations into electrical signals, which travel along the auditory nerve (the cochlear nerve) to the brain.

Problems at any point along this pathway cause hearing loss but the nature and location of the problem determines the type of hearing loss and, crucially, what can be done about it.

Conductive hearing loss – a problem in the outer or middle ear that prevents sound from being transmitted effectively to the inner ear. Usually treatable.

Sensorineural hearing loss – a problem in the inner ear (cochlea) or the auditory nerve. Often permanent, though manageable.

Mixed hearing loss – elements of both.

Common Causes of One-Sided Hearing Loss

Ear Wax Impaction

The simplest and most immediately treatable cause. Ear wax that becomes impacted in the ear canal physically blocks sound from reaching the eardrum. One side is often more affected than the other depending on canal shape, wax production, and whether cotton buds have been used to push wax deeper on one side.

The hearing loss from wax impaction is conductive the pathway beyond the wax is perfectly normal. Remove the wax and hearing returns immediately.

It’s mentioned first not because it’s the most serious, it’s the least but because it’s the cause most worth ruling out early. An ENT examination takes seconds to confirm or exclude it.

Middle Ear Infections and Fluid

Otitis media middle ear infection and its aftermath are among the most common causes of one-sided conductive hearing loss, particularly in children but also in adults.

Acute infection causes fluid to accumulate in the middle ear, muffling the transmission of sound through the ossicles. Persistent fluid after the infection has resolved glue ear (otitis media with effusion) can cause hearing loss that persists for months after the acute episode.

In adults, one-sided middle ear fluid that develops without an obvious preceding infection and particularly without the ear infections and colds that usually precede it in children can indicate Eustachian tube dysfunction, but should also prompt assessment to exclude a lesion in the post-nasal space that’s blocking the Eustachian tube opening. A nasopharyngeal mass including nasopharyngeal carcinoma can present this way, which is why adult-onset one-sided glue ear warrants specific investigation.

Perforated Eardrum

A hole in the eardrum from infection, trauma, a sudden pressure change, or a cotton bud inserted too far causes conductive hearing loss on the affected side. The size and location of the perforation determines the degree of hearing loss. Small perforations often close on their own. Larger ones may need surgical repair (myringoplasty).

Otosclerosis

Otosclerosis is a condition where abnormal bone growth in the middle ear fixes the stapes the smallest of the three ossicles in place, preventing it from vibrating normally. It causes progressive conductive hearing loss, typically starting in one ear (though it eventually affects both in most cases). It’s more common in women and tends to first appear in early to middle adulthood. It can run in families.

Otosclerosis is highly treatable, a surgical procedure called stapedectomy removes the fixed stapes and replaces it with a prosthesis, restoring vibration and hearing in the majority of cases.

Sudden Sensorineural Hearing Loss (SSHL)

This is the one that needs to be at the top of every list of one-sided hearing loss causes, because it’s time-sensitive and because it’s frequently dismissed or delayed.

Sudden sensorineural hearing loss is defined as a loss of 30 decibels or more across three consecutive frequencies, occurring within 72 hours. In practical terms, it’s a hearing loss that appears suddenly often overnight, sometimes with a “pop” sensation, frequently accompanied by tinnitus and sometimes dizziness.

Many people who experience SSHL assume it’s an ear blocked with wax, or that it’ll clear on its own, and wait days or weeks before seeing a doctor. This delay is directly harmful, SSHL is a medical emergency in the sense that treatment is most effective when started as soon as possible after onset, ideally within the first 24 to 72 hours.

The cause in most cases is not clearly identified a viral infection of the cochlea or auditory nerve, a vascular event reducing blood supply to the inner ear, or an autoimmune process are among the most commonly proposed mechanisms. Treatment is with high-dose oral corticosteroids, sometimes supplemented with intratympanic steroid injections directly into the middle ear.

Without treatment, around one third of patients recover spontaneously, one third recover partially, and one third have permanent hearing loss. With prompt treatment, recovery rates are significantly better. The window to act is measured in days, not weeks.

Sudden, significant hearing loss in one ear particularly with tinnitus needs same-day ENT assessment, not a wait-and-see approach.

Acoustic Neuroma (Vestibular Schwannoma)

An acoustic neuroma is a benign tumour growing on the vestibulocochlear nerve, the nerve that carries both hearing and balance signals from the inner ear to the brain. It grows slowly and causes a gradual, progressive sensorineural hearing loss in one ear usually accompanied by tinnitus on the same side and sometimes by balance difficulties or mild dizziness.

The hearing loss from an acoustic neuroma is typically unilateral, progressive, and may be subtle in the early stages. Because it develops slowly, patients often adapt around it before seeking assessment.

Acoustic neuromas are diagnosed on MRI, they appear as a mass in the internal auditory canal or at the cerebellopontine angle. Treatment options include observation with serial imaging for small tumours in older patients, stereotactic radiosurgery (Gamma Knife), or microsurgical removal, the approach depending on tumour size, growth rate, and patient factors.

The reason acoustic neuroma matters in the context of one-sided hearing loss is that it needs to be excluded in any patient with unexplained unilateral sensorineural hearing loss, particularly when the loss is progressive or accompanied by tinnitus. MRI of the internal auditory canals is the investigation.

Ménière’s Disease

Ménière’s disease affects the inner ear through abnormal fluid pressure causing episodic vertigo, fluctuating sensorineural hearing loss, tinnitus, and a feeling of fullness in the ear. It classically affects one ear, at least in its early stages.

The hearing loss in Ménière’s disease is characteristically fluctuating, it worsens during episodes and may partially recover between them. Over time, the hearing loss becomes more permanent as episodes accumulate.

One-sided hearing loss with associated episodic dizziness and tinnitus, particularly low-pitched tinnitus and low-frequency hearing loss should prompt assessment for Ménière’s disease.

Noise-Induced Hearing Loss One Side

Noise-induced hearing loss is usually bilateral from exposure to loud music, industrial noise, or firearms over time. But asymmetric exposure produces asymmetric loss. Firearm users develop more hearing loss on the side of the non-dominant hand (the ear closer to the muzzle). Musicians who perform in amplified settings may have more loss on one side depending on their position on stage.

Importantly, a single very loud noise exposure an explosion, a gunshot at close range, a sudden loud impact can cause immediate sensorineural hearing loss in one ear, sometimes accompanied by tinnitus. This is acoustic trauma, and like SSHL, it benefits from prompt assessment and treatment.

Autoimmune Inner Ear Disease

A less common but important cause the immune system attacks the inner ear, causing rapidly progressive sensorineural hearing loss that typically affects both ears but may start asymmetrically. The clue is the speed of progression hearing loss developing over weeks to months rather than years, in the absence of other identified causes. It responds to immunosuppressive treatment and is important to identify promptly because the progressive loss can be arrested with the right treatment.

Perilymph Fistula

A tear in the membrane separating the fluid-filled inner ear from the middle ear, usually from barotrauma (pressure change from flying, diving, or heavy lifting/straining). Causes sudden or fluctuating hearing loss alongside dizziness, with a history of the relevant precipitating event. Management ranges from rest to surgical patching.

Warning Signs That Need Prompt Attention

Some features of one-sided hearing loss need assessment without delay not at the next convenient appointment, but soon:

Sudden onset – any hearing loss that came on suddenly, overnight, or over hours. This is SSHL until proven otherwise and needs same-day assessment.

Rapidly progressive – hearing that’s noticeably worse week to week, even if the onset wasn’t sudden.

Associated with significant dizziness or vertigo – inner ear pathology affecting both hearing and balance simultaneously needs assessment to understand what’s driving both.

Tinnitus appearing alongside new hearing loss – particularly in one ear. The combination of new unilateral tinnitus and hearing loss is an indication for investigation.

Fullness or pressure in one ear without obvious cause – adult-onset unilateral ear fullness without a preceding infection or obvious cause warrants assessment.

Facial weakness or numbness – hearing loss accompanied by facial nerve weakness needs urgent neurological and ENT assessment.

Hearing loss after head injury – trauma can damage the cochlea, ossicles, or auditory nerve. Assessment after any significant head injury should include hearing.

What Does an ENT Do?

When a patient presents with one-sided hearing loss, the ENT assessment is structured to work through the possible causes systematically.

History – how did it come on (sudden, gradual, fluctuating), how long has it been present, are there associated symptoms (tinnitus, dizziness, ear pain, fullness, discharge), any relevant history (loud noise exposure, head trauma, previous ear infections or surgery, family history, medications).

Otoscopy – direct examination of the ear canal and eardrum. Wax, perforation, middle ear fluid, and eardrum abnormalities are visible here.

Pure tone audiometry – the most important investigation. A formal hearing test maps hearing thresholds across multiple frequencies in each ear separately. The audiogram pattern, which frequencies are affected, by how much, and whether the loss is conductive, sensorineural, or mixed is highly informative about the likely cause.

Tympanometry – assesses eardrum mobility and middle ear pressure. Flat tympanogram indicates middle ear fluid. Normal tympanogram with sensorineural loss points toward cochlear or nerve pathology.

Speech discrimination testing – assesses not just how loud sounds need to be to be heard, but how clearly speech is understood at a comfortable volume. Poor speech discrimination out of proportion to pure tone thresholds can be a clue to retrocochlear pathology, a problem with the nerve rather than the cochlea, which raises the index of suspicion for acoustic neuroma.

Acoustic reflexes – the middle ear contains a small muscle that contracts reflexively in response to loud sound. The presence or absence of this reflex, and its pattern across ears, provides additional diagnostic information.

MRI of the internal auditory canals – recommended for any patient with unexplained unilateral sensorineural hearing loss to exclude acoustic neuroma or other retrocochlear pathology. This is not optional investigation in the context of unexplained one-sided sensorineural loss, it’s standard.

Blood tests – where autoimmune inner ear disease, syphilis (a recognised cause of sensorineural hearing loss), or other systemic causes are suspected.

Treatment What’s Possible Depends on the Cause

Wax removal – immediate restoration of hearing in wax-related cases.

Middle ear fluid – observation, nasal treatment for Eustachian tube dysfunction, or grommet insertion if persistent.

Eardrum perforation – observation for spontaneous closure, or myringoplasty (surgical repair) for persistent perforations causing significant hearing loss.

Otosclerosis – stapedectomy or hearing aid.

SSHL – high-dose oral steroids started as soon as possible. Intratympanic steroid injection if oral steroids fail or can’t be taken. Hyperbaric oxygen in selected centres.

Acoustic neuroma – observation, radiosurgery, or microsurgery depending on size, growth rate, and patient factors.

Ménière’s disease – dietary management (low salt), diuretics, vestibular suppressants for acute episodes, and more invasive options for refractory cases.

Noise-induced/acoustic trauma – treatment for acute acoustic trauma with steroids; hearing aids and hearing protection for established noise-induced loss.

Autoimmune inner ear disease – corticosteroids and immunosuppressants.

Permanent sensorineural hearing loss – when the inner ear damage is permanent and doesn’t respond to treatment, hearing rehabilitation options include hearing aids for mild to moderate loss and cochlear implantation for severe to profound loss where hearing aids are insufficient.

When Should You See an ENT?

For any new or worsening one-sided hearing loss, particularly if it’s recent, sudden, or accompanied by other symptoms, the answer is soon. Not eventually. Not when it becomes more convenient.

The principle is straightforward: some causes of one-sided hearing loss are benign and easily treated, some are progressive but manageable, and a small number are time-sensitive. The only way to know which category applies is through a proper assessment. And the assessment audiometry, otoscopy, tympanometry is non-invasive, quick, and provides a great deal of clarity in a single appointment.

Final Thoughts

One-sided hearing loss is one of the most commonly under-investigated symptoms in ENT. People adapt around it, assume it’s not serious, and delay assessment until the loss is more established at which point some causes that were treatable early are harder to address.

The range of causes is broad from something as simple as wax to something as significant as an acoustic neuroma. The only way to know which it is, and what can be done about it, is to have it properly assessed.

Our ENT specialist evaluates one-sided hearing loss systematically from the initial examination and audiometry through to appropriate imaging and management planning. If hearing in one ear seems noticeably worse than the other and particularly if it came on suddenly or is accompanied by tinnitus or dizziness come in for an assessment sooner rather than later.