The loss of smell (anosmia) and distorted smell (parosmia) became common symptoms of COVID-19. These changes can be disruptive, affecting daily life and overall well-being. The sense of smell plays an important role in enjoying food, detecting dangers like gas leaks, and connecting with memories. Its alteration or absence can lead to frustration and impact quality of life.
The Typical Recovery Journey
Most individuals who experience COVID-19-related smell loss can expect their sense of smell to return. Approximately 90% see improvement within four weeks of infection. Around 80% regain their sense of smell within six to eight weeks. For most, recovery is gradual, with improvements continuing over several months.
Research indicates about 81% of adults with COVID-19-related smell loss recover within six months. Longer-term studies show over 95% of patients recover olfactory function within three years. While most people recover, a smaller percentage may experience persistent issues.
Understanding COVID’s Impact on Smell
COVID-19 affects smell by impacting supporting cells within the olfactory system. The virus does not typically infect olfactory sensory neurons directly, which detect odors. Instead, it targets sustentacular cells, which maintain olfactory neuron health and function.
These supporting cells express the ACE2 receptor protein, used by the virus to enter human cells. Damage to these cells can lead to inflammation in the olfactory epithelium, where smell receptors are located. This disruption can indirectly impair smell receptor function, leading to smell changes. The ability of these supporting cells to regenerate from stem cells explains why smell often recovers.
Strategies for Encouraging Smell Recovery
For those experiencing smell changes after COVID-19, smell training (olfactory training) is a recommended strategy. This involves regularly sniffing distinct scents to stimulate and help regenerate the olfactory system. A common approach uses four essential oils: rose (floral), lemon (fruity), clove (spicy), and eucalyptus (resinous or menthol).
The training involves smelling each scent for 10 to 20 seconds, twice daily, focusing on recalling the smell. This practice promotes neuroplasticity, helping the brain rewire olfactory nerve connections. Consistent smell training over several months improves smell function.
Addressing Persistent Smell Changes
When smell changes persist, individuals might experience conditions like parosmia or phantosmia. Parosmia is a distortion where familiar odors are perceived as unpleasant, such as rotten food or chemicals. This differs from anosmia (complete smell loss) and phantosmia (smelling odors not present).
Parosmia can be challenging, impacting food enjoyment and causing distress. While it often indicates recovery as olfactory nerves regenerate, it can last for months or years. If smell loss or distortion continues without improvement after two months, or worsens, consult an ear, nose, and throat (ENT) specialist.