What is it about ?
Smell is the sense that allows us to recognize smells. We have special cells in the nose that are sensitive to odors (olfactory cells) and pick them up. These olfactory stimuli are transmitted to the brain through the olfactory nerves. Once they reach the brain, they are converted into olfactory perceptions.
Odor disorders come in different forms
- A lack of smell (anosmia);
- A decrease in smell (hyposmia);
- Increased sensitivity to odors (hyperosmia);
- A disturbance of the sense of smell (dysosmia or parosmia).
Depending on the cause of the disorder, odor disorders are classified into two categories: transmission disorders and perception disorders.
- In transmission disorders, you cannot perceive smells because your nose is blocked.
- In perception disorders, the problem is with the nerves that run from the nose to the brain or that are in the brain.
The most common causes of smell disturbances are:
- a viral infection of the nose and sinuses of the face : it can also cause a swelling of the mucous membrane (transmission disorder) that damage the olfactory nerves (perception disorder);
- a bacterial infection of the nose and sinuses of the face ;
- swelling of the nasal mucosa due to allergic rhinitis or linked to nasal polyps ;
- chronic rhinitis.
Other causes are:
- trauma to the skull: it can damage the centers of smell in the brain, especially in the event of a blow to the back of the head;
- age: sensitivity to odors decreases with age;
- a brain tumor that damages the centers of smell;
- the migraine ;
- smoking;
- a disease, for example, a depression, the Alzheimer’s disease, the Parkinson disease, the diabetes ;
- congenital lack of smell (Kallmann syndrome);
- toxic substances ingested or inhaled (eg cocaine);
- more rarely, certain drugs (nasal corticosteroids, nasal decongestant sprays, certain antibiotics, certain cardiovascular drugs, antithyroid drugs).
One in four times, there is no cause for the loss of smell.
What is their frequency?
After the age of 53, 1 in 4 people have some degree of loss of smell.
The cause is a viral infection of the upper respiratory tract in 20 to 40% of cases, a problem with the nose and / or sinuses in 20 to 30% of cases, and head trauma in 10 to 20% of cases.
How to recognize them?
Smell has a great influence on the perception of taste. Before you realize that you smell less well, you will have often noticed that your food has less taste.
The signs can be:
- Not to smell any odor (anosmia);
- Smell less (hyposmia);
- Feeling that the smells are too strong (hyperosmia);
- Smell certain odors or perceive very unpleasant odors or odors that do not exist (dysosmia or parosmia).
The loss of smell associated with aging is so gradual that it goes unnoticed by the vast majority of people.
With swelling of the nasal mucosa, the nose is blocked and you breathe through your mouth. Once the mucous membrane has deflated through the use of a nasal spray or drops, you often find yourself smelling again. The loss of smell is often fluctuating: sometimes you no longer feel anything, sometimes you still smell a little.
When it is done following a head trauma, the loss of smell is usually permanent.
If your smell disorder is related to another disease, you also have the symptoms of those diseases.
How is the diagnosis made?
The doctor will first ask you how the symptoms started and how they evolved: have you had a respiratory infection? Have you completely lost your sense of smell or are you still smelling things? Did you have an accident ? Do you smoke ? …
He then examines the nose, throat and ear area extensively using a rhinoscope, an instrument that allows you to look inside the nose. He checks whether the structure of the nose is normal and whether it is not blocked, and whether there are, for example, signs of nasal polyps or chronic sinusitis. Mouth infections can give off bad smells. That is why a thorough check of the mouth and throat is also carried out.
If the doctor finds no cause for the smell disorder, he will refer you to the otolaryngologist (ENT) for further examinations. Odor disorder can be assessed in 3 ways:
- You must try to recognize the odors tested (identification tests);
- You have to tell if you feel something (cut-off tests);
- You have to differentiate between different smells (discrimination tests).
If necessary, the doctor will order additional imaging tests.
What can you do ?
If you notice a decrease in your sense of smell and / or sense of taste, contact your doctor. These disorders can indeed be due to different causes, so it is better to examine.
Stop smoking, because smoking has a negative influence on the sense of smell.
What can your doctor do?
Treatment depends on the cause. A stuffy nose usually responds well to medications (for example, a cortisone spray) or surgery (for example, for nasal polyps, chronic sinusitis, or deviated nasal septum). After a viral upper respiratory infection, you will often recover your sense of smell spontaneously, or at least partially. It may take several months.
According to recent studies, scent training can dramatically improve and speed recovery from infection. To do this, the patient must smell four different scents twice a day for at least six months.
There is no effective treatment for perceptual disturbances after trauma to the skull, although they may improve slightly with olfactory training.
Want to know more?
Are you looking for more specialized help?
- Smoking Assistance Center (CAF®) – FARES – Respiratory Affections Fund
- Tobacco specialists – FARES – Respiratory Affections Fund
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