Anosmia is the inability to smell, whether the instance is acute (temporary) or chronic (permanent). Any deviation in people’s ability to smell can adversely impact their quality of life and influence what and how much they eat, whom they talk to, and where they may go.
Olfactory dysfunction (reduced ability to smell) and anosmia (complete inability to smell) can have profound effects on a person’s quality of life. In fact, a sudden onset of anosmia can affect a person’s ability to cope emotionally and may lead to severe clinical depression, increasing the risk for suicide. A loss in olfactory function can arise from a variety of reasons with the most frequent causes being (1) upper respiratory tract infection (like a cold or a stuffy/runny nose), which can kill olfactory sensory neurons; (2) head trauma, which can sever olfactory sensory neurons axons; and (3) nasal and paranasal sinus disease, which can block airflow in the nasal passage. In a minority of cases, olfactory loss can arise from the inhalation of toxic chemicals, intranasal or intracranial tumors, and from congenital defects. Certain endocrine and psychiatric disorders have also been associated with a decrease or loss of olfactory function.
In some cases, a single nostril can lose the sense of smell. This may occur by an injury or minor trauma to the side of the head. The loss of smell to one side is called unilateral anosmia.
Signs, Symptoms, and Treatment
The loss of smell can be caused by multiple factors. Inflammation of the mucosal layer of the nasal passageway is the most common sign of acute anosmia. Inflammation can be caused by the common cold, flu, or allergies and may be resolved by anti-inflammatory medications, sleeping in a humidified room, and nasal sprays. There are three types of nasal sprays: decongestant, saline, and steroid. Decongestant nasal sprays work by reducing the blood vessel size in the mucosal layer of the nose that cause “stuffiness.” These can be purchased over the counter (without a prescription) but should not be used for more than three days in a row. Continual use can become “addictive” and reduce the spray’s effectiveness, resulting in a person’s cold or flu worsening. Saline nasal sprays thin the mucus within a stuffy nose, allowing it to be easier to blow your nose and remove the mucus buildup. These do not contain medicine—like decongestant nasal sprays—and can be used as often as needed. Finally, a health care provider may prescribe a steroid nasal spray for a patient to improve stuffiness caused by allergies. These should only be used as prescribed.
Chronic causes of anosmia are lesions to the olfactory system and polyps that develop in the nose. Lesions to the smell centers of the brain (especially the temporal lobes) or to the olfactory sensory neurons can cause permanent damage to the sense of smell. In congenital anosmia, a rare disease, an infant is born without the ability to smell. This can be life-threatening as the infant will have difficulty smelling its mother’s milk, which is necessary for survival. Polyps within the nose block the nasal turbinates, which in turn reduces airflow into the nasal passage. Nasal polyps are generally noncancerous and are thought to develop from chronic inflammation of the mucosal layer. Nasal polyps are often associated with allergies and/or asthma. Such polyps can be surgically removed if they are large enough to block the nasal passage and cause chronic sinusitis.
Jennifer L. Hellier
See also: Dysosmia; Interrelatedness of Taste and Smell; Olfactory Mucosa; Olfactory Nerve; Olfactory Sensory Neurons; Olfactory System; Phantosmia
Mayo Clinic. (2014). Loss of smell (anosmia). Retrieved from http://www.mayoclinic.org/symptoms/loss-of-smell/basics/definition/sym-20050804
National Institute on Deafness and Other Communication Disorders (NIDCD). (2013). NIH senior health: Problems with smell. Retrieved from http://nihseniorhealth.gov/problemswithsmell/aboutproblemswithsmell/01.html
National Institute on Deafness and Other Communication Disorders (NIDCD). (2014). Smell disorders. Retrieved from http://www.nidcd.nih.gov/health/smelltaste/smell.asp