Throughout the COVID-19 pandemic, it has become apparent that the coronavirus has an unusual effect on the sense of smell. This is likely because the initial place where the virus enters the body is through the nose.

Anosmia means loss or altered sense of smell and is one of the most common symptoms of COVID-19. It may be the first symptom to occur. Other symptoms, such as cough and trouble breathing, may occur later or may not occur at all. An altered sense of taste sometimes occurs along with loss of smell, which could also be a symptom of COVID-19.

Any loss of smell or altered sense of taste should be taken seriously, especially if it occurs suddenly and without any other symptoms like nasal congestion or allergies. Some people have also reported smelling unusual odors such as smoke or chemicals.

In large studies of people with COVID-19, anosmia is reported in over 50% of those who test positive on nasal swab. Many researchers around the world have found that loss of smell is a reliable predictor of coronavirus infection.

What causes anosmia?

Anosmia has been known for a long time to happen after infection with viruses, such as the one that causes seasonal flu.

Our sense of smell is largely controlled by nerves that sit on the interior lining of the nose, which transmit information about what you're smelling (such as flowers or smoke) to your brain.

When inflammation – say, from a virus – occurs, it can damage these delicate nerve endings and decrease their ability to transmit what external particles are telling the nose. As a result, there's no transmission of this information, which leads to anosmia.

Anosmia could be a symptom of coronavirus, but it can also be caused by other conditions such as:

• Rhinitis (inflammation in the nose)
• Nasal polyps
• Sinusitis
• Seasonal flu
• Seasonal allergies

How long will it last?

Most people with anosmia from COVID-19 will recover their sense of smell within two to four weeks. About 80% will fully recover after two months and 95% will recover after six months. If anosmia persists longer than six months, it is likely to be permanent.

While the long-term effects of COVID-19 are still not fully known, current evidence suggests that recovery of smell and taste may be similar to what happens with infection from other viruses.

What’s the treatment for anosmia?

If your sense of smell has not returned within two weeks, you can consider olfactory training, a low-cost treatment that you can try at home using essential oils that you can purchase at a drug store or through online retailers.

One common treatment strategy is to select four different scents (such as lemon, rose, clove and eucalyptus) and sniff each one for 10 seconds while imagining what it should smell like. This should be done twice a day for 12 weeks or until the sense of smell returns.

The goal of olfactory training is to force the brain to reestablish function of the nerves that carry the smells. While it is not always successful, it has potential to help and is essentially risk-free.

What should I do if I experience a loss of smell or taste?

People who lose their sense of smell or taste should get tested for COVID_19, self-isolate and stay home while waiting for test results.

To locate a COVID-19 testing center near you, visit this website

You might also consider booking a virtual visit via Ochsner Anywhere Care to further discuss your anosmia and any other nasal symptoms that might indicate other causes of smell loss.

The information in this blog post is accurate at the time of publication. However, as the situation surrounding COVID-19 continues to change, it's possible that information has changed since being published. While Ochsner Health is trying to keep our blog posts as up-to-date as possible, we also encourage readers to stay informed on news and recommendations by using the CDC website.

Editor's note: This blog was originally published on April 13, 2020 and has since been updated.