Loss of Smell: A Subtle Sign That Could Indicate Serious Health Issues

According to data from the CNRS (National Center for Scientific Research), around 5% of the population in France is affected by anosmia, name given to the total loss of smell. Although it only affects a tiny part of the population, anosmia is recognized as a real pathology, which is also highlighted each year on February 27, during World Anosmia Day, aimed at raising awareness of olfaction disorders.

One of the symptoms of the COVID was indeed the loss of smell, a first for the vast majority of contaminated people. However, people who have lost this sense are gradually finding him when the disease begins to heal, which is not the case with people affected by anosmia, where the loss of smell is final.

But what does a loss of smell really mean? The simplest explanation would be to say that it occurs when we are no longer able to feel anything, which can range from scent and scent of atmosphere to good dishes that we prepare.

In reality, a loss of smell is much more complex than that, and the process is largely not happening at the level of our nose, but at the level of the brain, in particular in the olfactory bulb area and the olfactory cortex. The first city represents the brain area which will receive the first signals of the fragrant molecules.

The olfactory cortex corresponds to the part of the brain which interprets the odors and allows us to recognize them by passing for example by memories. Jérome Lechien, ENT and surgeon of the head and neck and professor of surgery at the University of Mons, in Belgium, brings us more details concerning the path of odors.

“The smells of our environment are small molecules that will be attached to receptors in the upper part of our nose. The information received by the receiver will be transmitted inside the brain by transiting by several places, including the olfactory bulb which is a relay point and then the olfactory cortex which is in a way a dictionary of odors. When a disease or trauma affects receptors, or an area throughout the olfactory path, we speak of loss of smell ”

The loss of smell can have several causes

As we have specified, the loss of smell is a rather complex concept. But what is even more so are its causes. In its complete (anosmia) or partial (hyposmy) form, this symptom can result on the one hand, from an obstruction of the nasal cavity.

This is what can happen when you have a cold, a sinusitis or even if you make allergy. Having this obstruction will prevent odors from reaching the olfactory area.

And on the other hand, the second cause which can lead to a loss of smell is the head trauma. During road accidents, falls or aggressions, the shock may have suffered damage to the olfactory nerves, which connect the nose to the brain, even destroy them.

This is what happens in particular if the fascia cribriformis, Name given to the bone that separates the nose from the brain, fractures.

Viral diseases, such as covid or flu, are also causes to the loss of this sense. However, there is a more than strange link between the loss of smell and neurodegenerative diseases.

The serious illnesses to which it is linked

If the loss of smell is mostly associated with viral diseases, it may also be attached to even more serious diseases. Even more, it would be an early sign.

This is for example the case with Parkinson's disease. If the best known symptom of this disease is the involuntary and uncontrollable tremor, the majority of patients also have loss of smell. According to France Parkinsonup to 95 % of people with this neurodegenerative disease lose this meaning.

Same story for Alzheimer's disease. Indeed, the percentage of patients who suffers from an olfactory disorder is estimated at 80 % by the CNRS. In the case of these two diseases, the loss of smell would be an early sign, in particular due to the destruction of neurons caused by Parkinson and Alzheimer.

“The loss of smell can occur several years before the start of a dementia of Parkinson or Alzheimer. This is linked to a progressive destruction of neurons that take care of transmitting information from nose receivers to the center of smell, or even neurons from the center of smell itself “, explains Dr. Lechien.

The expert in ot-rhino-laryngology (ENT) also tells us that the loss of smell can also occur when a cerebral tumor, of a meningioma type, which forms from the membranes that surrounds the brain and the spinal cord (meninges), which will compress the olfactory paths, or when a person is suffering from diabetes.

Loss of smell, “A warning sign, a warning” next death

If you have been surprised to learn the link between the loss of smell and serious illnesses, the next information may surprise you just as much. In 2014, an American study published in the journal Plos One had been taken up by several media since it advanced that the loss of smell was a sign of death.

“It does not directly cause death, but it is a warning sign, a warning; She announces that something serious happened, that something has been damaged ”, had declared Professor Pinto, surgeon and specialist in olfaction and sinus disorders, in remarks reported by Science & Avenir.

If it was the first study on this subject, other more recent studies, published in 2022 and 2025, in the journal Jama Otolaryngology-Head & Neck Surgery, Confirmed that olfactory disorders were associated with an increased risk of 52 %increased mortality.

But how can the loss of smell really be linked to a higher risk of mortality?

“Several phenomena can explain this. Certain metabolic diseases, such as diabetes, can be associated with loss of smell, and therefore imply a risk of higher indirect mortality, that is to say linked to the underlying disease. The same reasoning can be applied, given the link between the loss of smell and neurological diseases ”, explains Dr. Lechien.

In addition, the loss of smell also exposes us to daily dangers, such as not detecting a gas leak or a start of fire at home. In these situations, the risk for life can be real.

However, it is impossible to assert that loss of smell is an early sign of death.

The advice of an expert if you have lost smell

As you can see, the loss of smell can be dangerous when it is part of the symptoms of a risk disease. But even if it is isolated, it can be disabling in our daily lives.

Indeed, the taste is closely linked to smell. When you eat, food smells enrich our taste perception. Without smell, the dishes may seem bland, even completely flavor.

Although few studies exist on this subject, specialists relate to the loss of smell with a reduction in libido, in particular due to a failure of the detection of chemicals such as pheromones.

Now that we know what a loss of smell is and that can mean, it is important to know which reflexes adopt to find it as quickly as possible.

Here are the advice of Dr Lechien:

– “Consult an ENT as soon as the loss of smell occurs so that it ensures that it is not a serious illness.”

– “Start” olfactory training “, by feeling familiar odors daily.”

Note that if the loss of smell persists after a viral disease or a cranial trauma, a treatment by injection of plasma rich in platelets (blood cells) can be proposed. It consists in taking a sample of the patient's blood, then extracting the platelets by centrifugation before reinjecting them.

Source: Elsan