Losing your sense of smell (anosmia) or experiencing a distorted sense of smell (parosmia or phantosmia) has been a widely reported symptom of COVID-19. Recovery is often possible, though the timeline can vary.
Typical Recovery Timelines
For most individuals, the sense of smell begins to return within a few weeks to several months after a COVID-19 infection. Studies indicate that around 90% of patients regain their olfactory function within two years. Some reports suggest that 72% of people recovered their sense of smell within one month, with recovery continuing for at least two years.
Recovery timelines can differ among individuals, influenced by several factors. These include the severity of the initial illness and age, with older individuals potentially experiencing a longer recovery. The specific COVID-19 variant involved may also play a role. While many see improvement quickly, a smaller percentage may experience prolonged or incomplete recovery, with some studies showing persistent olfactory dysfunction in a notable portion of patients even after one or two years. One study found 28% of patients still had persistent olfactory dysfunction at 24 months.
Understanding Smell Dysfunction
Smell dysfunction following COVID-19 can manifest in various ways. Anosmia refers to the complete inability to detect odors. Hyposmia describes a reduced sense of smell, where a person can detect some odors but with less intensity. Parosmia is a distorted sense of smell where familiar odors smell unpleasant or different, often described as burnt, chemical, or rotten. Phantosmia involves smelling something that is not actually present, such as phantom smoke or gasoline.
COVID-19 affects smell primarily by infecting specific cells within the nasal cavity. The SARS-CoV-2 virus does not directly infect the olfactory sensory neurons, which are responsible for detecting odors. Instead, the virus targets and infects the supporting cells, known as sustentacular cells, in the olfactory epithelium. These sustentacular cells are equipped with the ACE2 receptor protein, which the virus uses to enter human cells. Infection of these supporting cells can lead to inflammation or damage, disrupting their ability to support the olfactory neurons and potentially affecting the production of mucus that covers the olfactory epithelium, thereby impairing smell function.
Strategies to Regain Smell
Individuals seeking to aid their smell recovery have a primary, evidence-backed strategy known as “smell training,” or olfactory training. This method involves repeatedly smelling a set of strong, distinct odors daily to help retrain the brain and olfactory system. The rationale behind smell training is rooted in neuroplasticity, the brain’s ability to reorganize and form new neural connections, and the regenerative capacity of olfactory neurons.
To perform smell training effectively, individuals typically use four essential oils that represent different odor categories:
Rose (floral)
Lemon (fruity)
Clove (spicy)
Eucalyptus (resinous/menthol)
The process involves smelling each essential oil for about 10-20 seconds, twice a day, for several months. It is recommended to take a short break, one to two minutes, between smelling each scent. While engaging in smell training, it can be helpful to focus on memories or experiences associated with the specific smells to further engage the brain.
When to Consult a Doctor
It is advisable to seek professional medical advice for persistent smell loss, particularly if symptoms extend beyond a few months. While many cases of smell loss after COVID-19 resolve spontaneously, a doctor can help rule out other potential causes for the olfactory dysfunction. If significant smell loss persists for longer than two months and shows no signs of improvement, or if it is accompanied by other new or concerning symptoms, consulting a healthcare provider is recommended.
A doctor can provide further guidance, and in some instances, may refer patients to specialists such as an Ear, Nose, and Throat (ENT) doctor. Early evaluation can be beneficial, as there may still be potential for recovery or regeneration of smell function within a few weeks or months of the initial loss.