Loss of smell
Smell relies on specialised nerve endings high inside the nose that connect directly to the brain. They are among the few nerves in the body that can regenerate, which is why recovery is possible even many months after smell is lost.
Reduced smell is called hyposmia; complete loss is anosmia. Because flavour is mostly smell, most people also notice that food tastes bland.
Common causes
- Viral infections, including COVID-19, influenza and the common cold, which are the most common cause of sudden smell loss
- Chronic sinusitis and nasal polyps, which often improve when the underlying condition is treated
- Head injury, where the delicate smell nerves can be sheared as they pass through the skull base
- Ageing, and some neurological conditions
- Less commonly medications, smoking, toxins, or rarely growths, which is why examination matters
Will it come back?
After viral smell loss, most people improve substantially. The majority recover within weeks, and recovery continues for two years and sometimes longer.
During recovery many people experience parosmia, where familiar smells become distorted or unpleasant, so that coffee or onions smell burnt or chemical. Although unpleasant, parosmia is usually a sign of nerve regeneration and generally settles with time.
Smell training
Smell training is the main evidence-based treatment. It involves sniffing the same four familiar scents every day, and works like physiotherapy for the smell nerves, stimulating both the regenerating nerves and the brain pathways that interpret them. International guidelines recommend it, and studies show meaningful improvement in a majority of patients who persist with it.
It is done once or twice a day over about three months, then repeated with four new scents. Many people benefit from continuing for six to twelve months. Do not be discouraged if nothing seems to happen at first. Detecting anything, even faintly or in distorted form, is progress.
Where inflammation or polyps are contributing, treating the underlying sinus disease can restore smell. Most vitamins and supplements marketed for smell loss have no good evidence behind them.
Staying safe without smell
Smell is an alarm system. Make sure you have a working smoke alarm and change the batteries every six months. If your home uses natural gas, install a detector and use electric appliances where you can. Throw out any food you think might have spoiled and check use-by dates, because you cannot rely on the sniff test.
See a doctor promptly if you have
- Smell loss on one side only, or with one-sided blockage or bleeding
- Smell loss after a head injury
- Smell loss with headache, vision change, or clear watery fluid from one nostril
Patients under my care receive a detailed handout with the full smell training method, the scents to use, and the supporting evidence.
This page is general information and does not replace advice about your own case. Reviewed August 2026.