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Observations of patients with coronavirus showed that 80% of them experience impaired smell and partly taste. In the brain, the centers of taste and smell are located in the neighborhood. These anatomical features explain the loss of taste in all patients who have lost their sense of smell. They note the blandness of familiar dishes even with the addition of spices, sauces and marinades.
Why does the sense of smell disappear?
The causative agent of the SARS-CoV-2 coronavirus primarily attacks the respiratory system. In a matter of days, lymphocytes begin to release large amounts of cytokines (see coronavirus cytokine storm), which trigger devastating autoimmune reactions. The transmission of infection occurs by airborne droplets by inhalation of the smallest particles containing the pathogen. The entry gate for coronavirus is most often the nose, in the mucous membrane of which olfactory receptors are localized over a total area of approximately 5 cm². Each receptor has a corresponding neural pathway that connects to the center of the brain. Loss of smell occurs when these structures are affected by a virus.
The development of anosmia occurs in one of two ways:
The olfactory bulbs located in the nasal cavity are involved in the inflammatory process caused by the coronavirus. The receptors cannot perceive information about smells and tastes; therefore, it does not enter the centers of the brain. The process is accompanied by a pronounced mucosal edema, a feeling of nasal congestion, loss of smell, and difficulty in nasal breathing. Over time, these symptoms are accompanied by dry mouth, headache. The patient’s lips constantly dry up, a full-fledged night’s sleep is upset. Severe fatigue affects the ability to work and learning.
The virus immediately infects the center of the cerebral cortex that controls the perception of smells. The reverse process occurs – nerve impulses from the receptors enter the brain, but the return signal is not formed. A patient with coronavirus does not present complaints characteristic of rhinitis (mucus secretion, edema, difficulty breathing), but at the same time does not feel smells and tastes. There is an isolated shutdown of olfactory and gustatory sensitivity.
The patient ceases to perceive smells for 3-7 days after infection. Recovery of lost sensitivity occurs no earlier than 2 weeks. Most patients note that the loss of smell was the first symptom of a coronavirus infection that appeared after the incubation period. Almost 75% of patients claim that they have ceased to smell after the appearance of dryness in the nasopharynx.
After the loss of smell, there is a violation of taste perception. Those infected with the coronavirus say that any food becomes insipid. No matter what you eat – meat, fruits, spicy or sour dishes, everything is not tasty. Patients compare the process of eating with chewing paper.
Decreased susceptibility to odors manifests itself in one of the options:
Approximately 70 to 80% of patients with COVID-19 report a complete and immediate loss of smell. At the same time, taste perception is lost. Infected people do not feel not only light odors, but also sharp, saturated odors, for example, the smell of gasoline, ammonia. While eating, there are tactile sensations. Patients compare the use of the first courses with chewing water, and the second courses resemble cotton wool or paper in taste. Even those who did not eat spicy in a healthy state do not experience any specific sensations at all with the coronavirus.
The rest of the patients indicate a decrease in olfactory sensations. Smells are perceived dimly. In some cases, susceptibility to strong odors, such as garlic, is partially preserved, and more delicate aromas are completely lost, such as citrus.
If the sense of smell is preserved in whole or in part, olfactory hallucinations are possible. Patients report smelling rust in their noses or a rancid taste in food.
How long does the sense of smell disappear?
Numerous observations have shown that a period of loss of smell can be observed:
During periods of high temperature.
Throughout the disease without mucosal edema, discharge and feeling of nasal congestion.
Within 20-40 days, on average – up to a month after recovery.
Stable up to 6 months with gradual recovery.
Throughout life.
The duration of the absence of olfactory and gustatory sensations does not depend on what day they disappeared and on the severity of the symptom.
After recovery, paradoxical disorders of smell and taste can be observed. A number of people who have been ill indicate that with a lost or preserved sense of smell, they experience obsessive sensations:
Food staleness.
Rotten taste of saliva.
altered taste of dairy and meat products, the presence of a characteristic rancid or burnt taste.
A perverted sensation of smells and tastes may be present for up to three months after recovery.
Loss of smell does not always accompany coronavirus. This symptom manifests itself when the causative agent of the SARS-CoV-2 coronavirus affects the nerve pathways and the centers of the cerebral cortex responsible for taste and smell. Fortunately, this does not happen to every patient.
How many days does it return?
Coronavirus COVID-19 affects the olfactory nerves and bulbs reversibly. This means that the ability to recognize smells gradually returns. Most experts say that recovery takes from 2 weeks to 3 months. According to the findings of the European Archives of Otolaryngology, 25% of cases of coronavirus anosmia resolve within two weeks.
Somewhat different information is provided by the Centers for Disease Control and Prevention (CDC). Experts say that in those who have recovered from COVID-19, anosmia resolves in an average of 8 days.
Chairman of the Russian Respiratory Society Alexander Chuchalin notes that the return of olfactory sensitivity in some patients is observed in a short time from 3 to 7 days. As a rule, rapid recovery occurs after a mild form of coronavirus or when anosmia is the only symptom of the disease. Irreversible loss of smell is observed in a small proportion of patients, usually in the elderly.
The recovery period of smell after coronavirus depends on the severity of the damage to the corresponding receptors, nerve pathways and brain centers:
With the defeat of the nasal mucosa, susceptibility returns after 2-6 weeks.
If the pathogen has penetrated the cortical part of the analyzer, then recovery takes up to six months. An analysis of observations of patients with such injuries showed that the average rehabilitation period is 1-2 months.
[Video] Chief otolaryngologist of the Ministry of Health of the All-Russian State Television and Radio Broadcasting Company of the Bashkortostan State Television and Radio Broadcasting Company Elena Savelyeva talks about the loss of smell and taste due to coronavirus:
Could the sense of smell not return at all?
This question was exhaustively answered by an assistant professor of neuroscience at Harvard Medical School in an interview with a Medical Xpress journalist. According to professional opinion, damage to the olfactory nerves is always reversible: “Observations indicate that the body does not need to rebuild or replace olfactory receptors from scratch.”
The chief doctor of the Moscow ENT clinic, otolaryngologist Vladimir Zaitsev, in an interview with Ura.ru, says that after the coronavirus, the sense of smell may not disappear, but will decrease. After normalization of temperature, restoration of well-being, the risk of chronic hyposmia remains, in which the reduced perception of odors can be permanent.
Not all scientists support this point of view. COVID-19 is a new disease that is being studied. So far, the scientific medical community does not have enough data on the long-term consequences of infection. The Wall Street Journal published an article expressing concern that after suffering a severe form of coronavirus, there is still a chance of losing your sense of smell for life.
In other words, humanity has not yet gained the necessary experience to unambiguously determine the reversibility of anosmia after the coronavirus. The consequences of the disease are being studied, which means that new data will be published in the near future.
Doctors’ advice and recommendations
Doctors warn that in the event of anosmia, it is impossible to draw any conclusions on your own. Self-medication with loss of smell and taste is unacceptable. Atypical symptoms are the reason for contacting a specialist. Only a doctor will establish the root cause of the loss of taste and smell sensations. Further treatment depends on what caused the violations.
It is important to remember that anosmia may not be a sign of a coronavirus, but a serious disease of a non-infectious nature. Conclusions about the causes of loss of smell are made after laboratory diagnostics. According to the observations of otolaryngologist Alexei Koshelev, neurological causes of anosmia are detected in 1 out of 30 patients: “Yes, most patients with COVID-19 complain of loss of taste and smell. However, not every occurrence of anosmia is a symptom of the coronavirus.”
[Video] Dr. Komarovsky will talk about one of the typical symptoms of covid, explain why it is dangerous and share life hacks on how to train the receptors so that the sense of smell returns quickly: