- Symptoms & Onset
- COVID-19 Variants
According to recent studies, COVID-19 symptoms of loss of smell and taste typically begin 4-5 days after other symptoms have appeared and may last 7-14 days.
Symptoms often improve after 7 days, with more noticeable improvements after 14 days. While temporary loss of smell is also seen with the flu, it lasts longer with COVID-19.
Findings differ from person to person, and further research is needed to clarify when and why these symptoms occur.
How common is loss of smell and taste with COVID-19?
A study conducted on the evolution of symptoms of COVID-19 provided evidence that loss of smell or taste was one of the most frequent and persistent symptoms, with more than 1 out of 10 people reporting altered senses that persist even after all other symptoms have subsided.
Another study showed that COVID-19 patients with loss of smell and taste also had mood disorders such as anxiety and depression.
Although relatively minor symptoms, loss of smell and taste can negatively affect quality of life and cause significant frustration.
Why does COVID-19 cause loss of smell and taste?
The exact cause of the loss of olfactory senses due to COVID-19 is unclear. However, it is believed that it may be caused by damage to the cells that send signals to the brain regarding smell and taste. These cells are part of the olfactory epithelium in the nose and olfactory bulbs on the tongue.
A study at Harvard Medical School in Boston reported that the virus likely infects and damages sustentacular cells, which support sensory neurons in the nose.
This study concluded that SARS-CoV-2 attacks by targeting a receptor called ACE2 on the surfaces of cells. The sustentacular cells in the nose and some cells in the mouth have a substantial amount of ACE2 receptors. Olfactory senses are therefore lost as SARS-CoV-2 attacks these cells.
Another study reported that loss of smell and taste occurs concurrently with an increase in blood levels of an inflammation-signaling cytokine called interleukin-6. In addition, a postmortem study published last December reported symptoms of inflammation, such as leaky blood vessels, in the olfactory bulbs of people who had been exposed to COVID-19.
How is loss of smell and taste assessed in people with COVID-19?
Internationally recognized clinical tests are done to examine and diagnose any issues with olfactory senses. The tests use ordinary scents that are easily identifiable and familiar to the people undergoing the test.
For example, children are familiar with the smell of orange, mint, and vanilla and can identify them easily. Stronger scents of garlic, coffee, or phenyl ethyl alcohol or butyl alcohol are used to test adults. For testing at home, household items such as lemon, fragranced shampoo, or essential oils can be used to test for loss of smell.
Changes in smell can also affect taste. The four basic tastes may alter, making people feel that the food they are eating is tasteless. Some may lose taste completely while others may not feel satisfied after a meal because they do not enjoy the taste.
Can you regain lost sense of smell and taste?
Most people recover their sense of smell and taste within a few weeks. According to one study, 72% of people who experienced this symptom following COVID-19 regained their sense of smell and taste after a month. However, symptoms were more severe in other cases, with some patients not regaining their senses for months.
Some people stated that their sense of smell changed and that odors were unpleasant or different from what they remembered. This condition of altered sense of smell is known as parosmia, which may persist for months. It is believed that the reason behind this phenomenon may be the recovering of olfactory sensory neurons.
Several studies have reported that frequent short-term exposure to various scents can help people recover a sense of smell that was lost as a result of a viral infection.
What are the different variants of COVID-19?
The SARS-CoV-2 virus responsible for COVID-19 has gone through various evolutions over time, leading to different variants. According to the Centers for Disease and Prevention, SARS-CoV-2, Alpha, Beta, Gamma, Delta, and Omicron are considered variants of concern because they have affected the health of a large population globally, leading to significant increases in hospitalizations and death due to the complications.
New viral variants are usually considered more dangerous than previous variants due to the following:
- Increased transmissibility or unfavorable changes in COVID-19 epidemiology
- Increased virulence or a change in clinical illness presentation
- Decrease in the effectiveness of public health and social measures, as well as current diagnostics, vaccines, and therapies
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Do the COVID-19 variants cause different symptoms?
Loss of smell is more prominent in the Delta variant, although it may be observed in other COVID-19 strains. The Delta variant often presents with symptoms such as disorientation and diarrhea, unlike the Alpha variant, which presents mostly as the flu. The inability to maintain oxygen saturation is the most common feature in the Delta variant. Sore throat is a dominant symptom in the Omicron variant.
Every strain of COVID-19, however, may cause any of the above symptoms.
According to the Centers for Disease and Prevention, the most common symptoms of all COVID-19 variants include:
Other symptoms associated with COVID-19 include:
Although these symptoms are commonly seen among all the variants, some symptoms may be more severe, and others may be negligible or not be present at all.
Health Solutions From Our Sponsors
Onset and duration of symptoms of loss of smell/taste in patients with COVID-19: A systematic review: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7833280/#:~:text=The%20present%20study%20concludes%20that,occurrence%20of%20these%20symptoms.
Expression of the SARS-CoV-2 Entry Proteins, ACE2 and TMPRSS2, in Cells of the Olfactory Epithelium: Identification of Cell Types and Trends with Age: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7241737/
Clinical assessment of patients with smell and taste disorders: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118991/
Tracking SARS-CoV-2 variants: https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/
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