Loss of Taste and Smell in COVID-19 Infections

Smell and taste disorders have been reported in 34–98% of patients infected with COVID-19, either alongside other symptoms or on their own. Some background information is needed to understand the topic well.

Tastes such as bitter, sour and salty are detected by the taste buds on the tongue. Specific flavors such as coffee, melon or banana, however, are actually smells. Odor particles released while chewing food travel from the back of the throat to the nose, where they are detected by the olfactory cells at the very top of the nasal cavity and transmitted to the brain. This is why taste disorders caused by a loss of smell are rooted in problems in the nose.

Smell disorders mainly occur:

• With conditions that block airflow in the upper part of the nose (such as tumors, nasal polyps or heavy sinusitis discharge),
• When viral illnesses affecting the olfactory region (the common cold, COVID-19 and other infections) damage the nerve cells in this area,
• With certain diseases affecting the central or peripheral nervous system.

One study showed that COVID-19 patients are 27 times more likely to lose their sense of smell than patients with other viral upper respiratory tract infections. The smell disorder is characterized by being sudden, rapid and complete or nearly complete. There are different theories about its mechanism. It may sometimes appear as a distorted, unpleasant perception of odors (parosmia).

In the vast majority of patients it resolves completely. Recovery takes 7–10 days on average.

In patients who do not recover, systemic and/or topical (nasal spray) corticosteroid treatment may be given. Some studies have reported that sprays containing vitamin A may also be beneficial. If the problem does not resolve with treatment or on its own, smell training may be recommended. Smelling bottles of essential oils such as eucalyptus, clove or lemon several times every day is advised.