Many individuals who contract COVID-19 experience a temporary loss of their sense of smell, known as anosmia. Understanding the mechanisms behind this loss and typical recovery patterns can provide clarity for those affected.
How COVID-19 Affects the Sense of Smell
The SARS-CoV-2 virus, which causes COVID-19, primarily impacts the olfactory system indirectly, rather than by directly infecting odor-detecting neurons. Research indicates the virus targets supporting cells, specifically sustentacular cells, within the nasal cavity lining. These cells possess ACE2 receptors, allowing viral entry and disrupting the environment needed for olfactory neurons.
When these supporting cells are affected, it leads to inflammation and damage within the olfactory epithelium, the tissue containing smell-sensing neurons. The dysfunction of their surrounding support structures impairs the neurons’ ability to transmit smell signals to the brain. This disruption accounts for the sudden and often complete loss of smell experienced by many COVID-19 patients.
Recovering the Sense of Smell
For most people who experience smell loss due to COVID-19, the sense eventually returns, though the timeline varies. A majority see their smell return within a few weeks to a few months after acute infection. Studies suggest about 80% to 90% of individuals regain their sense of smell within six months.
Some individuals experience prolonged recovery, and for a smaller percentage, smell may not fully return or may manifest as distorted perceptions. Conditions like parosmia, where familiar smells are distorted and often unpleasant, can emerge during recovery. Phantosmia, where individuals perceive smells not actually present, is another less common phenomenon. These altered smell experiences are thought to result from regenerating olfactory nerves attempting to rewire themselves, sometimes imperfectly, as the system heals.
Supporting Smell Recovery
Individuals can support smell recovery through olfactory training, commonly known as smell training. This involves regularly sniffing a set of strong, distinct odors to stimulate the olfactory system and encourage nerve regeneration. Kits include four distinct scents, often essential oils like rose, eucalyptus, lemon, and clove, representing different odor categories.
To perform smell training, sniff each scent for about 20 seconds, twice daily, focusing on recalling the smell. Consistency is important, and this practice should continue for several months. While smell training does not guarantee full recovery for everyone, it is a non-invasive method that can help improve outcomes. If smell loss persists or is accompanied by other concerning symptoms, consulting a healthcare professional for guidance is advisable.