Loss of smell, medically known as anosmia, is a frequent symptom associated with COVID-19, often manifesting abruptly. This sensory alteration has emerged as a distinct indicator of SARS-CoV-2 infection, leading to questions about its causes and duration.
Smell Loss as a COVID Symptom
Smell loss is a common characteristic of COVID-19, affecting a significant percentage of infected individuals (30-80%), often alongside taste disturbances. This symptom can appear early, often serving as an initial sign. In some instances, anosmia may be the sole symptom, particularly in mild or asymptomatic cases. COVID-19 related smell loss often differs from impairment during a common cold or flu. Unlike other viral infections, which typically cause smell loss due to nasal congestion, COVID-19 can lead to anosmia without such obstructions, making this unique presentation a diagnostic clue for SARS-CoV-2 infection.
The Science Behind COVID-Related Smell Loss
The SARS-CoV-2 virus primarily affects specific cell types within the nasal cavity, disrupting smell. Research indicates the virus does not directly infect olfactory sensory neurons, the nerve cells detecting odors. Instead, it targets supporting cells, known as sustentacular cells, found in the olfactory epithelium, which are crucial for providing metabolic and structural support. Viral entry into these supporting cells is facilitated by the ACE2 receptor protein and TMPRSS2 enzyme on their surface, allowing the virus to gain access and initiate infection. This infection of non-neuronal cells leads to an inflammatory response within the olfactory epithelium, and this inflammation and damage to the supporting cells indirectly impair olfactory sensory neuron function, disrupting their ability to transmit smell signals to the brain.
Recovery and Lingering Smell Changes
For many, COVID-19 related smell loss is temporary, with recovery typically occurring within weeks to a few months. Most people regain their sense of smell within 60 days of recovering from the initial infection, though the duration and quality of recovery can vary significantly. Beyond complete loss, individuals may also encounter other smell dysfunctions. Parosmia is one such condition, where familiar odors are perceived as distorted or unpleasant. Another related condition is phantosmia, characterized by smelling odors that are not actually present, and these altered smell perceptions can be a challenging aspect of post-COVID recovery, indicating that the olfactory system is still undergoing changes.
Managing Smell Loss
For individuals experiencing smell loss or distortion, several strategies can help manage the condition and potentially aid recovery. Smell training, also known as olfactory training, is a widely recommended method involving regularly sniffing a set of distinct essential oils, such as eucalyptus, lemon, clove, and rose, for short periods each day. The repeated exposure to these different scents helps to stimulate and re-educate the olfactory system over time. While smell is impaired, it is important to take certain safety precautions, such as being vigilant about potential hazards like gas leaks or spoiled food. If smell loss persists for an extended period or significantly impacts daily life, consulting a healthcare professional is advisable, as they can offer further guidance and assess whether additional interventions or investigations are necessary.