Anosmia & Hyposmia
Loss of smell.
Smell is the sense people notice least until it goes. Losing it changes food, safety and mood, and it has more causes than most people expect. Some of them are treatable in the nose; others are not, and the assessment exists to tell the two apart honestly.
General education only. Your diagnosis, options and coverage are individual, and are established at your consultation.
The Condition
Where smell comes from, and where it fails.
Odours reach a small patch of nerve endings high in the roof of the nose, and from there the signal travels through the base of the skull to the brain. Smell can fail at any point on that path. If air cannot reach the patch, because polyps, swelling or a severely deviated septum block the way, the loss is called conductive, and it is the kind an otolaryngologist can most often do something about. If the nerve endings themselves are damaged, by a viral infection, by a head injury that shears the nerve fibres where they pass through the skull, or by the slow changes of ageing, the loss is sensorineural, and recovery depends on the nerves' own capacity to regenerate.
Most people who say they have lost their sense of taste have in fact lost smell. The tongue registers only sweet, salt, sour, bitter and savoury; everything that makes food taste of something in particular is smell, reaching the nose from behind while you eat. A distorted sense of smell, in which familiar things smell wrong or foul, is called parosmia, and phantom smells with no source are phantosmia; both are common during recovery from viral loss and are usually a sign of nerves regrowing rather than of anything sinister.
The pattern of loss says a great deal. Smell that comes and goes, or that improved during a course of steroids, points to a nasal cause. Loss that arrived abruptly with a cold or with COVID-19 points to the nerves. Loss after a blow to the head, loss on one side only, or loss with headaches, visual change or nosebleeds needs imaging, because the rare causes that matter are found there.
Patterns worth describing at consultation
- Gradual loss with a blocked nose, fluctuating from day to day
- Sudden loss with a viral illness, with or without a blocked nose
- Loss after a head injury
- Familiar foods or smells that now seem distorted or foul
- Smells that no one else can detect
- Loss on one side only, or with headache, visual change or bleeding
Having several of these does not confirm the diagnosis, and having few does not exclude it. The examination does that.
Why It Happens
The common causes, and the rare ones.
In an otolaryngology clinic the most common treatable cause is chronic rhinosinusitis, particularly nasal polyps, which sit exactly where odours need to go. Viral infections are the most common cause overall; the coronavirus pandemic made that familiar to everyone, but other respiratory viruses have always done the same thing. Head injury is the third large group. Beyond those: normal ageing reduces smell gradually; some medications and toxic exposures blunt it; a few people are born without it; and reduced smell is recognised as an early feature of some neurological conditions, though on its own it is not a diagnosis of any of them, and most smell loss has an ordinary explanation.
Rarely, smell loss is the first sign of a growth in the nose or at the base of the skull. Those cases are the reason a one-sided loss, or loss with other symptoms, is imaged rather than watched.
Nasal causes are treatable
When polyps or inflammation block the path, treating them often restores smell, sometimes quickly.
Viral loss often recovers
Many people recover over weeks to months as the nerves regrow. Some recover partially, and some do not; distortion along the way is common.
Injury is less predictable
Recovery after head injury is possible but less reliable, because the nerve fibres may be severed rather than inflamed.
Safety comes first
Anyone without smell should have working smoke and gas detectors and a habit of checking food dates, because the nose can no longer warn them.
Assessment First
How smell loss is assessed.
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History
When it started, how suddenly, what came with it (a cold, an injury, a blocked nose), whether it fluctuates, whether it ever responded to steroids, and what it has cost you.
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Nasal endoscopy
A direct look at the roof of the nose and the sinus openings: polyps, swelling, discharge, a mass, or a clear passage, which itself is informative.
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Smell testing
A standardised identification test that measures how much smell is present rather than relying on impression, and gives a baseline against which change can be judged.
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Imaging, when the pattern calls for it
CT of the sinuses when sinus disease is suspected; MRI when the loss is one-sided, followed injury, is unexplained, or comes with neurological symptoms.
Your Options
What can be done, and what can't.
The options depend entirely on the cause, which is why the assessment comes first. Set out side by side so you can weigh them yourself.
| Option | What it involves | Trade-offs to weigh |
|---|---|---|
| Treating a nasal cause | Corticosteroid in the nose, saline irrigation and, for polyps, surgery or biologic therapy as the disease warrants. Smell is one of the outcomes these treatments are measured by. | Only helps when the loss is conductive. Improvement can be quick, but it depends on keeping the inflammation controlled afterwards. |
| Smell training | Deliberately sniffing a small set of strong, distinct odours twice a day for several months, concentrating on each. Used after viral loss and head injury, where evidence supports a modest benefit and there is no risk. | Slow, and it asks for daily persistence. It improves the odds of recovery; it does not guarantee it. |
| Medication | A short course of oral corticosteroid is sometimes used when inflammation is suspected, and treats any nasal cause at the same time. | Limited evidence for nerve-related loss on its own, and side effects with repeated use. Used selectively, not routinely. |
| Time, and safety | After viral loss, many people recover over weeks to months without any treatment. Meanwhile, smoke and gas detectors, food-date habits and telling the people you live with are the practical protections. | Uncertain, and the waiting is hard. Follow-up smell testing shows whether recovery is happening even before it is obvious. |
There is no proven treatment that restores smell in every case, and the practice will not offer one. What it offers is an accurate diagnosis, treatment of what is treatable, and a clear account of what recovery can reasonably be expected.
When not to wait
Loss of smell with a head injury that caused loss of consciousness, with a severe or persistent headache, with visual change, with numbness of the face, with bleeding from one side of the nose, or with clear watery drainage from the nose, should be assessed promptly. Go to the nearest emergency department for any of these after an injury.
Common Questions
Loss of Smell, answered plainly.
It depends on the cause. When polyps or inflammation are blocking the path, treating them often restores smell. After a viral infection, many people recover over weeks to months, some partially, and a minority not at all. After head injury, recovery is possible but less reliable. Smell testing at intervals shows whether recovery is happening, which is more useful than guessing.
The evidence supports a modest benefit after viral loss and head injury, with no risk, which makes it worth doing. It involves smelling a small set of strong, distinct odours deliberately twice a day for several months. It is slow, and it improves the chances rather than guaranteeing the result.
Almost always, yes. The tongue registers only the basic tastes; the flavour of food is smell, reaching the nose from behind as you eat. A true loss of the basic tastes is rare and points to different causes, so the two are distinguished at consultation.
When polyps or blocked sinuses are the cause, surgery that clears them often improves smell, and it is one of the reasons patients pursue it; a lasting decrease is also possible, and that risk is discussed. Surgery cannot restore smell lost to nerve damage from a virus or an injury, and it is not offered for that.
Reduced smell is recognised as an early feature of some neurological conditions, but on its own it is not a diagnosis of any of them, and the great majority of smell loss has an ordinary cause: sinus disease, a viral infection, an injury, or age. If the assessment finds nothing in the nose and the pattern raises the question, that is discussed openly and, where appropriate, your physician is asked to look further.
Assessment first. Then the options are yours.
An OHIP-insured assessment begins with a referral from your physician or nurse practitioner. The office contacts you once it is received.