Anosmia is the inability or decreased ability to smell. It can be permanent or temporary, depending on the cause.
In this article, we review the definition, symptoms, and causes of anosmia, as well as how it may relate to COVID-19. We also discuss how doctors may treat this condition.
Anosmia is the inability to smell. Some people
Experts suggest that anosmia and hyposmia affect about
Sometimes people call anosmia smell blindness. The condition may be permanent or temporary.
Smell is a complex process that
These nerves line the olfactory epithelium, which is the tissue lining the nasal cavity. When odor molecules from the environment stimulate these nerves, they transmit signals to the brain.
The brain receives the olfactory information and processes it into a scent that a person can identify.
When people develop anosmia, they may notice that they can no longer smell identifiable odors.
On the other hand, people who were born with anosmia due to genetic differences may not recognize they have anosmia, because they never had the ability to smell.
Neurodegenerative diseases, such as Parkinson’s disease and Alzheimer’s disease,
If people living with neurodegenerative diseases recognize a loss of the sense of smell, they should seek medical evaluation as soon as possible. Sometimes anosmia is the earliest sign of neurodegenerative diseases.
When a person can no longer smell, they are unable to sense warning odors in foods and the environment. People living with anosmia may experience a lower quality of life related to social interactions, eating, and feelings of well-being.
- inherited anosmia
- older age
- chronic sinonasal diseases, which affect the nasal cavity or the nasal sinuses
- severe head injury
- upper respiratory infections
- neurodegenerative diseases
Some people may inherit anosmia, which means they have it from birth. Healthcare professionals refer to anosmia not associated with any other condition as isolated congenital anosmia (ICA).
As people age, their sense of smell decreases. People may also lose the ability to discriminate between different smells.
Experts suggest that possible
- decreased nerve fibers and receptors in the olfactory bulb, a part of the brain responsible for processing scent
- loss of sensory cells in the nose
- deterioration in the central nervous system cognitive processing functions
Chronic sinonasal diseases
People with chronic sinonasal diseases may have one of two
Conductive sinonasal disease refers to conditions that affect airflow, such as:
- nasal polyps
- sinonasal tumors
- allergic rhinitis, or hay fever
- septal deviation
People with neurosensorial sinonasal disease may have damage or dysfunction along the nerve pathway between the nose and brain. Some conditions that
Upper respiratory infection may contribute to
- illicit drugs
- toxic vapor
Some neurodegenerative diseases that may cause anosmia or some degree of loss of smell include:
- Parkinson’s disease
- Alzheimer’s disease
- Huntington’s disease
- amyotrophic lateral sclerosis
Sometimes doctors are unsure why a person developed anosmia. This is known as idiopathic anosmia.
General health exams do not typically include olfactory or smell testing. To detect whether a patient has anosmia, a doctor needs to rely on them to self-report a loss of or change in their ability to smell.
In general, experts
Improving health questionnaires
The National Health and Nutrition Examination Survey (NHANES) self-reported olfactory function index offers a
Through this survey, doctors
When deciding on the most appropriate treatment for a person living with anosmia, doctors must choose a therapy that
People with genetic disorders may want to look into treatment
If a person developed anosmia following an infection, doctors
People with post-traumatic olfactory disorders resulting from a head injury
Surgery or corticosteroid drugs
Doctors may find it challenging to predict whether surgical methods can help with anosmia. However, endoscopic sinus surgery
Some cases of anosmia may also resolve spontaneously without treatment. This can occur in about
Some people living with anosmia
Part of the issue is that some people living with anosmia
People living with anosmia
Mealtime may also be
Anosmia can also be dangerous. Normally, a person’s sense of smell can inform them of environmental dangers, such as a gas leak or the presence of smoke. The ability to smell spoiled food or poisonous liquids can prevent a person from accidentally ingesting toxins.
People living with Alzheimer’s or Parkinson’s disease may develop severe complications from anosmia, including malnutrition, safety problems, and increased mortality risk.
The novel coronavirus responsible for the COVID-19 pandemic
These symptoms occur early in the disease and may sometimes be the only recognizable symptom in people with the SARS-CoV-2 virus.
In studies researchers did earlier in the COVID-19 pandemic, they reported that anosmia occurred in about
A hypothesis for why some people with a SARS-CoV-2 infection develop anosmia is
If research can support this hypothesis, it
People with a SARS-CoV-2 infection
Anyone who recognizes a loss of or change in their sense of smell should contact a doctor. Depending on the cause of anosmia, doctors may select different treatments. These
If a person thinks they may have been exposed to the novel coronavirus or are experiencing symptoms of COVID-19, they should self-quarantine and call their local public health office for instructions.
Although losing the sense of smell, or developing anosmia, does not appear to be life threatening, the complications can be dangerous.
Smell allows people to recognize a dangerous environment or spoiled food, and people living with anosmia lose this ability.
Smell also provides pleasure. Smelling the scent of delicious food, fresh air of the countryside, or the sensual scents of intimate moments enhances a person’s everyday experiences. People who recognize they have lost their sense of smell may experience a lower quality of life.
Doctors have identified several causes of anosmia. Some causes can lead to permanent or temporary loss of smell. Choosing the most appropriate treatment requires an accurate diagnosis of the cause of anosmia.