Loss of Smell: Detailed Guide

Author: Op. Dr. Javidan Asafov · ENT / Otolaryngology Specialist · Last medical review: 19.10.2026

How is smell perceived?

The special nerve cells that detect smell are found in a small area of lining (the olfactory epithelium) at the very top of the nasal cavity, level with the space between the eyes. When odour molecules in the air we breathe reach this area, they dissolve in the thin layer of mucus covering the lining and bind to receptors at the tips of the nerve cells. The fine fibres of the stimulated nerve cells pass through a thin, perforated layer of bone that forms the roof of the nasal cavity and reach the olfactory bulb on the underside of the brain. From there, the signal is passed on to the areas of the brain involved in smell, memory and emotion.

An important feature of olfactory nerve cells is that, when damaged, they can be renewed from stem cells in the nose. The improvement seen over time in many people with loss of smell is linked to this ability to regenerate. Smells reach the nose by two routes: with the air breathed in through the nostrils, and, while eating, with the air that rises from the mouth through the throat to the back of the nose. The second route creates the aroma of food. This is why people with loss of smell often complain that they cannot taste; yet the basic tastes detected by the tongue, such as sweet, salty, sour and bitter, are usually preserved.

Types of smell disorder

Smell disorders are named according to how much the sense of smell has decreased or how it has changed. More than one type can be present in the same person at the same time.

• Hyposmia: a reduced sense of smell. Smells are noticed more weakly, later or only when they are strong.
• Anosmia: complete or almost complete loss of the sense of smell. The cooling or burning sensation that some pungent substances, such as mint or ammonia, create in the nose may be preserved, because it is detected by a separate nerve; this does not mean that the sense of smell has returned.
• Parosmia: a smell is perceived differently from how it really is, usually in an unpleasant way. Coffee, onions, fried meat or toothpaste may smell burnt, rotten or like something chemical. Although it can make eating difficult, it often appears during the recovery phase of post-viral loss of smell and tends to lessen over time.
• Phantosmia: sensing a smell when there is no source present; a burning, smoky, chemical or rotten smell is commonly described. It is often seen together with post-viral or nose- and sinus-related smell disorders. A bad smell that is really present, caused by inflammation in the sinuses, is distinguished from this on examination.

Conductive and nerve-related causes

The causes of loss of smell are considered in two main groups. This distinction guides the choice of treatment.

Conductive loss of smell

Here the olfactory nerves are intact, but odour molecules cannot reach the olfactory area. The most common causes are chronic sinusitis and nasal polyps. Polyps are non-cancerous swellings that develop as a result of long-standing inflammation of the lining, and they can fill the upper part of the nasal cavity, where the olfactory area is located. In chronic sinusitis, the inflammation does not only narrow the airway; it can also directly affect the olfactory epithelium, which is why the sense of smell can decrease even without marked blockage. In allergic rhinitis and non-allergic nasal inflammation, swelling of the lining also reduces the sense of smell. A bend in the septum, the central wall of the nose (deviated septum), and enlarged turbinates (turbinate hypertrophy) rarely cause complete loss of smell on their own, but they can contribute by reducing airflow. This type of loss of smell often gets better and worse along with nasal blockage and usually responds well to treatment.

Nerve-related loss of smell

This occurs when the olfactory nerve cells, the olfactory fibres or the smell pathways in the brain are affected. Viral infections, head injury, ageing, smoking, contact with certain chemicals and some medicines fall into this group. Rarely, a person is born without a sense of smell. In some people, no clear cause is found despite a detailed assessment. In nerve-related loss of smell, the nasal examination is usually normal. Both types may be present together in some people.

Loss of smell after a viral infection (including COVID-19)

A sense of smell that does not return after an upper respiratory tract infection such as a cold or flu has passed, even though the nose has cleared, is one of the most common causes of loss of smell. The virus disrupts the function of the olfactory system by affecting the olfactory nerve cells and the cells that support them. With the COVID-19 pandemic, this condition was seen in many more people and became better recognised; in COVID-19, loss of smell can start suddenly, without marked nasal blockage.

In many people with post-viral loss of smell, the sense of smell returns fully or partly over time; smell training can support this process. In some people recovery is quick, while in others it is slow and gradual; because the olfactory nerves take time to regenerate, patience is needed. Parosmia or phantosmia may appear during recovery; although this can be distressing, it is often seen during the recovery process and tends to ease over time.

Head injury

Blows to the head, particularly in falls and road accidents, cause the brain to move suddenly inside the skull. When this happens, the delicate olfactory fibres passing through the thin layer of bone in the roof of the nose can be stretched or torn; the smell areas of the brain can also be affected. Loss of smell is sometimes noticed later, because in the early period the person is focused on their other injuries. Recovery after a head injury may be slower and more limited than after a viral infection; even so, meaningful improvement is seen over time in some people, and smell training can be supportive during this process.

Age-related decline

Like sight and hearing, the sense of smell gradually declines with age. As we get older, olfactory nerve cells are renewed more slowly, the nasal lining becomes thinner and the small openings in the bone through which the olfactory fibres pass may narrow. Because this decline develops very slowly, most people do not notice it; in later life, enjoying food less than before, loss of appetite and adding too much salt to food may be the first signs. Here too, the doctor checks whether correctable causes, such as nasal blockage, sinusitis or medicines being taken, are also present.

Links with neurological diseases

A reduced sense of smell can occur in some neurological diseases, such as Parkinson’s and Alzheimer’s disease, and this reduction can sometimes appear before other symptoms. This information may worry people with loss of smell; however, the great majority of cases of loss of smell are due to nose and sinus disease, previous infections or age. In neurological diseases, loss of smell is usually significant not on its own but in combination with other symptoms.

Examination and tests

Assessment starts with a detailed history: you will be asked when the loss of smell started and whether it began suddenly or gradually, whether you had a cold, flu or COVID-19 beforehand, and about nasal blockage, discharge, allergies, head injury, smoking, contact with chemicals and the medicines you use. Whether smells are perceived in a distorted way is also important.

The inside of the nose is then examined endoscopically with a thin camera. This examination shows polyps, signs of sinusitis, swelling of the lining, enlarged turbinates and a deviated septum, and it allows the doctor to assess whether the olfactory area is open. The extent to which the sense of smell is affected can be measured with standard smell tests based on detecting, distinguishing and identifying different smells. These tests give a result that can be compared over time and help to monitor recovery.

If sinusitis or polyps are suspected, a CT scan of the sinuses may be requested where necessary; the CT scan shows how extensive the disease is and helps with planning if surgery is being considered. For loss of smell that develops after a head injury, that has no clear explanation or that is thought to be nerve-related, an MRI scan may be requested where necessary. Imaging is not needed for every case of loss of smell.

Treatment options

Treatment is planned according to the cause of the loss of smell; your doctor decides which medicine to use and how. Stopping smoking and keeping away from chemicals that can damage the olfactory system are beneficial whatever the cause.

Loss of smell due to blockage and nasal inflammation

In loss of smell due to sinusitis, polyps and allergy, the aim is to reduce swelling of the lining so that air can reach the olfactory area. Intranasal corticosteroid sprays or drops are the main treatment and are used regularly as recommended by the doctor. Because the olfactory area is in the upper part of the nose, holding the head in a suitable position during use can help the medicine reach this area; the correct technique is demonstrated during the examination. Rinsing the nose with saline clears away secretions and supports the effect of the medicine. Decongestant nasal sprays give short-term relief, but long-term use can lead to medication-induced congestion.

Loss of smell after a viral infection

For post-viral loss of smell, there is no medicine with sufficiently demonstrated effectiveness that directly speeds up the regeneration of the olfactory nerves. Smell training forms the basis of treatment, and this method is recommended in international guidelines. If there is accompanying nasal inflammation or allergy, intranasal corticosteroid sprays or drops and rinsing the nose with saline can be added. Caution is needed with methods and products whose effect has not been proven.

How is smell training done?

Smell training aims to support the regeneration of nerve cells and to help the brain recognise smells again by stimulating the olfactory system regularly. Usually a few clearly different smells are chosen, such as rose, lemon, eucalyptus and clove; essential oils or spices you have at home can also be used. It is done as follows:

• Prepare the smells: put each smell in a separate small jar or bottle with a lid and write its name on it. Do not apply essential oils to your skin or inside your nose.
• Sniff with focus: bring the jar close to your nose and sniff it for a short time with calm, gentle breaths.
• Remember the smell: while sniffing, picture in your mind how you used to perceive that smell; for example, while sniffing lemon, imagine cutting a lemon.
• Be consistent: continue the training regularly over several months; its effect appears over time.

It is common to smell nothing at first or to perceive smells in a distorted way, and this is not a reason to stop the training. After a while, the smells can be changed and the training continued with new ones. Smell training is a harmless method that is easy to do at home.

The role of surgery

Surgery has a place only in conductive causes of loss of smell; it has no role in nerve-related loss of smell due to a virus, head injury or age. For nasal polyps that do not shrink despite medical treatment and for chronic sinusitis, endoscopic sinus surgery opens the natural drainage pathways of the sinuses, removes the polyps and restores airflow to the olfactory area. Because polyps can recur over time, regular care with intranasal corticosteroid sprays or drops and saline rinses continues after surgery as well.

If a markedly deviated septum or enlarged turbinates that do not shrink with medicines restrict airflow, septoplasty or turbinate reduction can make breathing easier and help sprays reach the inside of the nose better. The effect of these procedures on the sense of smell varies from person to person; the decision on surgery is made by considering the cause of the loss of smell together with the examination and CT findings.

Quality of life and safety

Although the sense of smell is often taken for granted, losing it can noticeably affect quality of life. Not enjoying food can lead to a reduced appetite or, conversely, to eating saltier, sweeter and fattier food. A person may feel anxious about not being able to notice their own body odour; losing favourite smells can cause a feeling of unhappiness. It is reassuring to know that loss of smell is a well-known condition that often tends to improve.

The following measures are recommended for everyday safety:

• Gas and smoke: keep a gas alarm and a smoke detector at home and check their batteries regularly. Make sure the hob and oven are switched off after use.
• Food: pay attention to use-by dates; write the date on food you have opened or cooked, and do not eat food you are unsure about.
• Cooking: do not leave the hob unattended for long, and use a timer. Spices, lemon and foods with different textures can make meals more enjoyable.
• Personal care: use perfume and deodorant in moderation; when needed, ask someone you trust for feedback.

Frequently asked questions

Does loss of smell go away? This depends on the cause. Loss of smell due to sinusitis, polyps or allergy often improves with treatment; with polyps, regular care is important because symptoms can recur over time. In post-viral loss of smell, too, the sense of smell returns fully or partly over time in many people; smell training can support this process. In loss of smell due to head injury or age, recovery may be more limited; even so, assessment and smell training can be helpful.

I haven’t been able to smell since having COVID-19. Will it get better? In most people with loss of smell after COVID-19, the sense of smell returns fully or partly over time; in some people recovery is quick, in others slow. Continuing smell training regularly can support recovery. If there has been no improvement for a long time, an examination is recommended to see whether there is another, accompanying cause in the nose.

Everything smells bad. What does this mean? Distorted, unpleasant perception of smells is called parosmia and is often seen during the recovery phase of post-viral loss of smell. It usually appears while the olfactory system is recovering and tends to ease over time. During this period, avoiding foods that trigger parosmia, such as coffee, onions or fried meat, for a while and eating food lukewarm or cold can bring relief.

Does smell training really work? Smell training is a method whose benefit has been shown in research, particularly in post-viral loss of smell, and it is recommended in international guidelines. It may not be equally effective for everyone; however, it is harmless, easy to do at home and, when done regularly, can contribute to recovery.

Can loss of smell be a sign of a serious disease? The great majority of cases of loss of smell result from nose and sinus disease, previous infections or age-related changes. A reduced sense of smell can also occur in some neurological diseases, but this is a rare cause. Do not put off an examination if your symptoms are on one side of the nose, if there is blood in the discharge or if other new symptoms accompany them.

Will surgery bring back my sense of smell? If loss of smell is due to a cause that blocks airflow to the olfactory area, such as polyps or chronic sinusitis, endoscopic sinus surgery can improve the sense of smell in many people. Surgery has no role in nerve-related loss of smell due to a virus, head injury or age; in this case, smell training and follow-up come first.

This article is for general information; please consult your physician for diagnosis and treatment.