If you can’t smell a thing, it’s time you found out why. Dr Mel Wynne-Jones shares her explanation...

Sense of smell

Smell gives us pleasure (or not!), and is important for tasting food, detecting dangers (smoke, gone-off food), and even sexual attraction. Around 12 million receptors inside our noses send signals along our olfactory nerves to our brains so we can detect around 10,000 different odours.

Close links with brain areas responsible for memory and emotion mean smells can also activate powerful memories – good and bad.

Nasal congestion

Virus infections – common colds – invade delicate nasal linings that swell, triggering sneezes and a tickly throat, and disabling our smell receptors. Our noses feel blocked but run with clear fluid that turns green as infection-fighting cells and bacteria move in.

Our sinuses (air-filled spaces behind the nose) often get congested, too, making us feel unwell and muzzy-headed.

Cold remedies containing paracetamol, caffeine and/or decongestants can help, as can nasal decongestant sprays (use for no more than a week), steam inhaling or decongestant chest rubs. Check with your pharmacist if you have other medical conditions or take other medication.

Allergies

Pollen, pet hair and other allergens can cause nasal congestion, itchy/watery eyes and/or wheezing, so avoid your triggers if you can (visit pollenuk.info).

Decongestants and anti-allergy treatments, such as antihistamine tablets/nasal sprays, eye drops and nasal steroid sprays, can help, but you may need asthma treatment or even preventive injections for severe symptoms.

Allergies can also trigger nasal polyps (pale, benign fleshy growths that block the nostril); they may improve with steroid nasal sprays or need to be removed using a general anaesthetic.

Chronic sinusitis

This can be linked to bacterial/fungal infection, allergies, polyps, smoking, diabetes, nasal dryness, swimming (especially diving), dental decay, immune system problems or (rarely) a tumour. It’s more common if your nose or facial bones have structural problems, such as a deviated nasal septum (distorted dividing cartilage between the nostrils), from birth or after an injury.

Your sinuses can’t drain properly, and you may lose your sense of smell, as well as noticing catarrh, headaches, a post-nasal drip (pale or green mucus at the back of your throat), bad breath, and/or a cough.

See your GP if symptoms last more than a couple of weeks (see ‘5 Tests You May Need To Have’).

Treatment is aimed at the underlying cause; you may be offered surgery to ‘trim’ fleshy tissues over your septum, straighten your nose or drain your sinuses.

Brain disorders

These can affect the way we interpret smells; our smell/taste senses also become less sensitive as we get older. We may lose our sense of smell completely after a head injury, or if we develop a brain tumour, Alzheimer’s disease or Parkinson’s disease.

Epilepsy, particularly temporal lobe epilepsy, can trigger ‘false’ smells or hallucinations.

Ways to cope if you lose your sense of smell

Up to a fifth of people who lose their sense of smell don’t regain it. Be sure to tell your employer if this could affect safety at work.

You may need to ask other people whether food is safe to eat (stick to use-by dates), and get a natural gas detector, as well as a smoke alarm. You could even lose interest in food, so take care to eat as healthily as possible and use colour and texture to boost ‘meal appeal’.

Fifth Sense (fifthsense.org.uk) provides information and support for people with smell or taste problems, including ‘smell training’.

5 tests you may need to have if you’re losing your sense of smell

1. Blood tests for signs of infection, allergy or rarer causes.

2. X-rays, MRI scans or CT scans to show facial bones, sinuses and the back of the nose.

3. Endoscopy (telescope examination) of the nose and sinuses.

4. A mucus sample to test for bacterial or fungal infection.

5. Brain scan (this is rarely needed).