The coronaviruses are responsible for the respiratory disease COVID-19.

Since its discovery in late 2019, the coronavirus has led to more than 6.45 million deaths worldwide and more than 1 million deaths in the United States.

COVID-19 can lead to severe or life threatening illness, especially in older adults, people who are not vaccinated, and people with weakened immune systems. Most people with COVID-19 develop mild symptoms.

Loss of smell and taste are the most reported symptoms. Other common symptoms of COVID-19 include:

People with certain genes may lose taste or smell more often. Scientists are looking at this association. We know a lot about the link.

Loss of smell and loss of taste are commonly reported COVID-19 symptoms. Researchers are continuing to examine why some people with COVID-19 develop these symptoms while others don’t. Recent evidence suggests genetics may play a role.

Among 32,142 people with COVID-19 in a 2021 review of studies, 38.2% of them developed loss of smell while 36.6% developed loss of taste.

In a 2022 study, researchers collected data on COVID-19-related loss of smell or taste from surveys from 69,841 people. Researchers found that 68% of people reported one of these symptoms.

Researchers found that certain location variants of the UGT2A1 and UGT2A2 genes expressed in the olfactory epithelium were associated with COVID-19-related loss of smell. Your olfactory epithelium is a thin layer of tissue along the roof of your nose that helps you smell.

These genes play a role in metabolizing substances that make you smell. It is not clear how and why these genes influence smell loss.

Several possible reasons people with COVID-19 develop loss of smell have been hypothesized, but the exact cause isn’t clear. Possible mechanisms theorized to contribute include:

  • There is obstruction of the airway.
  • Damage to olfactory cells.
  • The olfactory centers in the brain have been damaged.
  • The cells supporting olfactory cells are malfunctioning.
  • The olfactory cells have inflammation-related functions.

Experimental evidence suggests damage to the cilia in your nose and olfactory epithelium contribute to loss of smell in people with COVID-19, but not infection of the nerves in your brain that help you smell. Cilia are tiny hairs that help clear away mucus.

Evidence shows that the coronaviruses enters and accumulates in olfactory support cells through angiotensin converting enzyme 2 and transmembrane protease serine 2. Your ability to smell can be impaired by the breakdown of these cells.

In a 2021 review of 45 studies including 42,120 people with COVID-19, researchers found that people severely ill or hospitalized for COVID-19 had a lower chance of experiencing loss of smell than those who were not severely ill or hospitalized.

In the 2022 study mentioned above, researchers found:

  • Women reported losing smell or taste more often than men.
  • “The average age of people who reported losing their smell or taste was 41 years, compared with 45 years for people who didn’t experience these symptoms.”
  • people of East Asian descent and African Americans were significantly less likely to develop these symptoms than people of European descent

Who is most likely to lose their sense of smell and taste is the topic of this article.

In a 2021 study involving 67 people with COVID-19, 74.6% recovered their sense of smell an average of 60 days after developing COVID-19. The remaining 25.4% had persistent smell loss that lingered beyond 60 days.

Another 2021 study found that 96.1% of a group of 97 people with COVID-19-related loss of smell recovered by 12 months, which was about 10% more than had recovered at 6 months.

In a 2021 review of 17 studies, researchers found that the average duration of smell and taste disorders was 7.5 days, plus or minus 3.2 days, in a group of 79 people with COVID-19. Meanwhile, 40% of people recovered completely within 7.4 days, plus or minus 2.3 days.

People with COVID-19 lose their sense of smell for a long time.

Within a couple of months most people regain their sense of smell or taste. Some people have effects that can last for a year or more.

“Your doctor may recommend olfactory training if your smell doesn’t return.”

Olfactory training involves repeatedly sniffing scents for 20 seconds each at least twice a day for 3 months or more. Common scents include lemon, rose, cloves, and eucalyptus.

Research suggests that olfactory training can be an effective treatment for COVID-19-related smell loss.

Steroids and high doses of omega-3 fatty acids may be recommended by some doctors. These are effective for treating smell loss from non-viral causes.

One small 2020 study found evidence that omega-3s helped protect the sense of smell in people undergoing nasal surgery. The ability of omega-3s to treat COVID-19-related smell loss remains theoretical.

Additionally, intranasal vitamin A has also been recommended as a possible therapy that may help with olfactory regrowth.

Visit your doctor if you or your child have lingering symptoms that persist about 4 weeks or longer after you develop COVID-19.

Your doctor can suggest tests that can help identify the root cause of your symptoms.

“Symptoms of COVID-19 include loss of taste and smell. Some people develop these symptoms and others don’t, so researchers are trying to understand why. Evidence suggests genetics may contribute.”

In particular, researchers have identified UGT2A1 and UGT2A2 as genes linked to COVID-19-related smell loss. More research is needed to understand exactly what role these genes play.