Sudden loss of smell: 3 causes of anosmia

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For many mammals, a keen sense of smell is essential for survival. Most mammals rely on their noses to detect environmental hazards, identify food to eat, or locate prey. Although the human sense of smell is no longer evolutionarily important, we still have to rely on our sense of smell to detect bad foods or environmental hazards like fire and gas. This allows us to distinguish 10,000 odors. And how exactly does the human sense of smell work?

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In our nasal mucosa, in the region of the roof of the nose, there is a special area equipped with special olfactory cells. This area is called the olfactory mucosa and has about 10 million olfactory cells. Olfactory cells are nerve cells that absorb odors from the environment via delicate sniffing hairs. Once an odor molecule binds to an appropriate receptor on a sniffing hair of an olfactory cell, the olfactory cell releases a special electrical signal. This signal is transmitted directly to the brain via the olfactory nerves, where it is processed and interpreted in the olfactory bulb, a small bulge at the frontal base of the brain.

Our ability to smell therefore largely depends on the error-free functioning of olfactory cells and olfactory nerves. However, if these cells are dysfunctional, our olfactory system can fail completely. These causes can cost us our sense of smell.

These 3 causes can trigger anosmia

Viral respiratory infections

One of the most common causes of transient anosmia is respiratory infections. Even a simple cold can alter the olfactory cells in the roof of the nose so badly that signals are no longer sent to the brain. Also, when you have a cold, the mucous membranes in your nose swell. It is difficult for us to breathe because the narrow nasal airways are blocked. If the fresh air no longer reaches the olfactory cells, these cannot of course transmit any olfactory information.

Loss of smell is especially common with COVID-19 infection. Anosmia is now considered one of the main symptoms of the disease. The viruses cause severe inflammation of the olfactory cells and supporting cells in the roof of the nose. Sometimes the cells die and are not regenerated. Then, the severe limitation of smell or the total loss of smell is sometimes permanent.

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In diseases of the central nervous system, nerve cells in the brain die. Besides the effects on the motor function of the muscles, one of the most common symptoms of the disease is a reduced sense of smell, which can go as far as the complete loss of smell. In fact, researchers have found that the loss of sense of smell in many people with Parkinson’s occurs years before typical symptoms of the disease. Upon closer examination, it was found that the olfactory bulb in the brains of those affected by the neurological disorder was only about half the size of people who did not have Parkinson’s disease.

nasal polyps

Nasal polyps are benign growths of the nasal lining. They grow out of the mucosa in the turbinates as droplets and are connected to the mucosa by a tissue stalk. Depending on the size of a polyp or the number of such polyps growing in the paranasal sinuses, nasal breathing can be severely restricted. Less fresh air at the level of the olfactory cells then also means the loss of the sense of smell. Nasal polyps also often cause headaches and a feeling of pressure in the middle of the face.

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