Anosmia, why does the loss of smell happen and how to recover it?
Published: 15 March, 2022 - Updated: 23 May, 2022 | 5'
What is anosmia, the loss of the ability to smell?
The Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL-CCC) defines anosmia as the total loss of the sense of smell, which can be congenital or acquired. 7
Human beings can smell between 4 and 10,000 different scents. Despite its implications, smell is a sense that is sometimes forgotten as it is not considered as important as other senses. However, loss of smell affects millions of people around the world. At least one in five adults suffers from some olfactory disorder, according to a review of SEORL-CCC studies. 2,3,5
Kinds of anosmia and their durability
Depending on the duration of anosmia, a difference can be made between temporary and chronic loss of smell.
This is a total loss of the sense of smell that lasts for a period of time.
This is a total loss of smell that is permanent.
How anosmia is diagnosed
The diagnosis of people suffering from anosmia should be made by a specialist, based on a medical history and the necessary diagnostic tests.
Depending on its cause, it may be useful to perform olfactometry, a set of tests that measure olfactory capacity by exposure to a series of smells with scores on different scales to produce a sensory map.
Other olfactory disorders
Hyposmia, partial loss of sense of smell
Hyposmia is the reduction of the sense of smell.
Parosmia, unpleasant smells
Parosmia is a distortion of the sense of smell in which a pleasant smell is perceived as unpleasant.
Cacosmia, olfactory hallucinations
Cacosmia is a distortion of smell in which an unpleasant scent is sensed without the existence of odour molecules in the environment.
Phantosmia, phantom smells
Phantosmia refers to the experience of smells that do not exist.
Causes of anosmia
Post-viral olfactory loss (PVOL) is one of the most common causes of decreased olfactory ability. Pathogens include viruses that cause the common cold, such as influenza, parainfluenza, rhino and coronavirus. In such cases, nasal congestion and a transient loss of smell are present.
The presence of viruses affects the ability of the olfactory epithelium to spread odorant particles to the olfactory receptors, thus preventing the decoding of odours within the olfactory bulb, and decreasing or eliminating the “olfactory memory“.4
Reduced olfactory capacity can also be caused by trauma, nasal conditions (such as allergic rhinitis or chronic rhinosinusitis with or without polyposis), previous nasal surgery such as deviated nasal septum, specific medications, or neurodegenerative diseases such as Parkinson’s syndrome or Alzheimer’s disease.7
One of the most uncommon cases is called congenital anosmia. It has been found in a range of sexual developmental anomalies and has been reported in family cases. It represents 3% of the causes of olfactory loss. Regarding congenital anosmia secondary to other pathologies, the most common is Kallmann syndrome, which includes gonadotropic hypogonadism and anosmia.9
Finally, other causes of anosmia include destruction of olfactory neuroepithelial cells, which can be caused by inhaling toxic chemicals.5
Consequences of losing your smell
Smell plays a key role in everyday life and, like taste, is considered a chemical sense that provides basic information about the environment.
It affects food and nutrient intake choices, as it involves appetite regulation, relationships and the detection of potentially toxic and dangerous substances, and can therefore warn of certain risks.
Its loss can therefore be frustrating for the person suffering from it, affecting, among other things, their ability to enjoy food, recognise their own personal smell and fragrances, and reduces the recall of memories associated with smell, resulting in a significant impact on quality of life.7
In addition, reduced ability to smell can be dangerous due to the inability to detect noxious chemicals, smoke and spoiled food.1,9
Studies show that between 25% and 33% of patients with reduced olfactory ability have symptoms of depression, while 27% to 30% report severe distress on quality of life surveys.6
How to overcome anosmia
For the diagnosis and treatment of anosmia, medical advice should always be taken. The treatment of anosmia will depend on the cause.
Can smell be recovered?
In those individuals with loss of smell that remains after a viral infection process, the ability to smell can be improved by repeated exposure to different smells.
This technique is known as smell training, and is a safe, scientifically proven procedure that works well for people with post-viral anosmia.7
How long can the process of recovering smell take?
The process can take several months (the guidelines and duration may be different depending on the instructions of the medical specialist).
Aromas to train the sense of smell
Olfactory training” is a self-management strategy that consists of a regular programme of using strong smells or essential aromas to activate the memory of the olfactory system.
Olfactory training with Essential Oils is a valid strategy recognised by several societies as an adjuvant in the recovery of olfactory and taste capacities.
A recent analysis of 10 clinical studies of olfactory training, which included more than 600 subjects, showed recovery rates of between 30-60% of olfactory capacity.
Likewise, another study showed that repeated exposure to smells can improve olfactory sensitivity as assessed by electroencephalograms and brain activity recordings related to olfactory events. This suggests that olfactory training alone may lead to some improvements in smell function.6
Exercises to recover smell
The recommendation of olfactory training has three key premises:
- Firstly, that it be implemented under specialist medical supervision.
- Secondly, it is an adjuvant in the integral management of the recovery of the olfactory capacities of the person with anosmia.
- And thirdly, it should be used in individuals with olfactory loss of more than 2 weeks.
The main exercises to train the sense of smell consist of exposing the individual to different essential aromas of varying intensity by using olfactory strips. These oils train the sense of smell with the aim of identifying smells, storing them and remembering them.
Can olfactory training be done at home?
It is possible to carry out the olfactory training plan at home under the advice of a doctor.
What smells are used to recover the sense of smell?
As a good strategy for olfactory and taste training are aromas composed of high quality essential oils, which are in the categories Floral, Fruity, Herbal and Resinous/Balsamic.
- Absent. https://abscent.org/.
- Angelucci, F. L. et al. Physiological effect of olfactory stimuli inhalation in humans: an overview. International Journal of Cosmetic Science, 2014, 36, 117–123.
- Fifth Sense: Smell, Taste & Life. https://www.fifthsense.org.uk/.
- Hopkins, C. et al. Management of new onset loss of sense of smell during the COVID-19 pandemic – BRS Consensus Guidelines. Clinical Otolaryngology. 2021;46:16–22.
- Mateos, C. et al. El olfato, el sentido olvidado. Al menos uno de cada cinco adultos sufre trastornos de olfato. Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. Madrid, 26 de mayo de 2016.
- Pekala, K. et al. Efficacy of olfactory training in patients with olfactory loss: a systematic review and meta-analysis. Int Forum Allergy Rhinol. 2016 March; 6(3): 299–307.
- Sociedad Española de Otorrinolaringología y Cirugía de Cabeza y Cuello. https://seorl.net/anosmia-perdida-olfato/
- Waizel, H.S. et al. Anosmia congénita. Reporte de un caso. An Med (Mex) 2014; 59 (2): 142-147.
- Walker, A. et al. Anosmia and loss of smell in the era of Covid-19. BMJ 2020;370:m2808.