Loss of Smell (Anosmia): Causes, Treatment and Recovery

How does the sense of smell work?

Odour molecules travel up the nose to a small patch of olfactory tissue high in the nasal cavity. Nerve cells there send signals to the brain via the olfactory bulb. Most of what we call “taste” is actually smell: the tongue detects only sweet, sour, salty, bitter and umami, while flavour comes largely from smell. So when smell fails, food seems bland.

Complete loss is called anosmia, reduced smell is hyposmia, and distorted smell (such as everything smelling burnt) is parosmia.

Main causes

Nasal blockage: colds, allergic rhinitis, chronic sinusitis and nasal polyps, a deviated septum.
Viral infections: colds, flu and Covid-19, which can damage the olfactory neurons and supporting cells.
Head injury, which can sever the olfactory nerves.
Ageing: smell declines gradually, especially after 65–70.
Medicines: some antibiotics, blood pressure drugs and others.
Smoking, toxins and cocaine.
Neurological disease: Parkinson’s disease and Alzheimer’s disease often cause early loss of smell.
Other: hormonal disorders, radiotherapy, nutritional deficiencies, rare tumours.

Smell loss after Covid-19 and other viruses

Post-viral smell loss is one of the most common causes in adults. After Covid-19, many people regain their sense of smell within weeks to a few months, but a minority have persistent loss or parosmia lasting a year or more. Recovery is often gradual and incomplete in the beginning. Smell training and treating associated nasal inflammation are the best-supported actions, and the AAO-HNSF consensus recommends an ENT evaluation if loss persists beyond a few weeks.

Smell training

Smell training is a simple, low-risk programme in which you sniff a set of strong odours twice a day for at least 3–6 months. A typical kit includes four scents: rose (floral), lemon (fruity), clove (spicy) and eucalyptus (resinous). Sniff each for about 20 seconds, concentrating on the memory of the scent, and rest for 10 seconds between them. Studies show it improves smell in many people with post-viral and other types of loss, though results vary.

Be consistent: daily practice matters more than the exact scents.
Change the scents every 3 months if you wish.
Make a note of improvements; progress may be slow.

Medical treatment

Treating nasal disease: nasal steroid sprays, saline rinses, allergy treatment, treatment of sinus infection and removal of polyps or surgery for structural blockage.
Short courses of oral steroids in selected cases of chronic sinus disease.
Review medications that may impair smell.
Smell training for post-viral, post-traumatic and age-related loss.
Other options under study (platelet-rich plasma, vitamin A drops) are not yet standard; discuss with a specialist.
Supplements: zinc and vitamin B are not proven to help in people without a deficiency.

Staying safe and eating well

Fit smoke alarms and gas detectors, and check them regularly.
Label food and check dates; do not rely on smell to check if food is spoiled.
Use timers when cooking to avoid burnt food.
Add texture, temperature, colour and spice (chilli, lemon, pepper) to make food more enjoyable.
Take care with cleaning products and gas appliances.
Smell loss is linked to low mood and loss of appetite; reach out for support if this affects you.

What an ENT assessment involves

The specialist asks about onset, associated symptoms and medicines, examines the nose with a small camera to look for polyps, swelling or infection, and may order smell tests, a CT scan of the sinuses or an MRI of the brain and olfactory bulbs, depending on the history. Blood tests may be done to look for underlying conditions.

When to see a doctor

Smell loss lasting more than 2–4 weeks.
Loss with a blocked nose, facial pain or discharge that does not resolve.
Loss in one nostril only, or associated with bleeding.
After a head injury.
With memory problems, tremor or other neurological symptoms.
Distorted smells (parosmia) that affect eating.

Three common situations

No smell since a cold two weeks ago: common; use saline rinses and start smell training, and review if no improvement at 4 weeks.

Gradual loss with a blocked nose and polyps: an ENT assessment can find treatable inflammation.

Smell loss after a fall on the head: seek assessment; recovery is less likely than after a virus, but some improve.

Key points to remember

Loss of smell is often temporary. Treat nasal inflammation, start daily smell training, keep safe at home and consult an ENT specialist if it persists beyond a few weeks, is one-sided or follows a head injury.

This guide is for general information and does not replace an assessment by your own doctor or ENT specialist.

Questions about loss of smell

These answers are general information and do not replace an examination or individual medical advice.

How long does loss of smell last after a cold or Covid?

Many people recover within weeks to a few months; a minority have longer-lasting loss.

Does smell training work?

Studies show it improves smell in many people with post-viral and other types of loss, though results vary.

Is loss of smell a sign of a serious disease?

Usually not, but it can be an early sign of some neurological conditions, so persistent unexplained loss should be assessed.

Can I lose my sense of taste too?

Often yes: most of what we perceive as taste is smell, so food seems bland.

Can nasal polyps cause loss of smell?

Yes, they block airflow to the smell area and are a common treatable cause.

Should I take zinc?

Zinc has not been shown to restore smell in people without a deficiency.

Sources

This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.