Anosmia is the complete inability to detect odors.
Kayla was born with a condition called congenital * anosmia that left her unable to smell any odors. At first Kayla did not realize that she was different from other people. Later, when she did, she pretended that she could sense odors the same way other people did because she did not want to be different. Kayla was eight before her parents realized she had no sense of smell.
Sometimes food was a problem for Kayla. One mean girl played a trick on her and gave her spoiled milk to drink. Kayla could not smell that the milk was sour, so she drank it; but when she tasted it, she spit it out all over herself. As Kayla got older, she became anxious about her personal hygiene because she could not smell her own body odor. Some days she was depressed about her hidden disability, but she tried to remind herself that having no sense of smell is not a life-threatening problem and not nearly as limiting as being blind or deaf.
People with anosmia cannot smell odors. This condition can be temporary or permanent. Some people are born without the ability to smell, whereas others develop this condition later in life. Although through normal aging many people's ability to smell gradually weakens, aging rarely causes a total loss of this sense. It is difficult to tell how many people have anosmia. Estimates are that about 2 percent of Americans have a noticeably reduced sense of smell, although not all have completely lost their ability to smell.
In order to have a sense of smell, three factors must be present:
Any time that one of these three factors is absent or interrupted, individuals may have a decreased ability to smell or in certain cases may lose their sense of smell completely.
Certain conditions can also lead to a permanent blockage of the nasal * cavity so that air cannot reach the odor receptors. This situation can occur when a person has nasal polyps * . A birth defect or an injury to the nose can also block the nasal cavity.
Damage to the odor receptors can occur from infection with certain viruses. These receptors can also be permanently damaged by inhaling chemicals, either accidentally or intentionally (e.g., snorting cocaine or inhaling paint thinner). Endocrine * (hormonal) disorders can also damage odor receptors. In addition, some people, through an error in prenatal development, are born without odor receptors and never have the ability to smell. Often these people have other congenital defects as well.
Damage to nerves that carry information from the odor receptors to the brain and that process odor information in the brain can occur in many ways. These include the following:
Even though there are many known explanations for why individuals develop anosmia, in about one-fourth of cases doctors cannot find a specific reason why the sense of smell has been lost.
Diagnosis begins with a complete medical history, physical examination, and review of all medications being taken. Many tests may be done to look for conditions that could be causing the anosmia. Some of these tests are a complete blood count; an analysis of the function of various endocrine (hormone-producing) glands; and x-rays or CT scans * of the head. In some cases a biopsy (tissue sample) may be taken from the nose and examined under a microscope.
Two tests are commonly used to measure the amount and type of smell loss. The Connecticut Chemosensory Clinical Research Center (CCCRC) test has two parts. In part one, the patient is asked to sniff a bottle with plain water and one with the chemical butyl alcohol and then is asked to identify the sample with an odor. Each nostril is tested separately. In the second part, the patient is given 10 samples of common smells such as cinnamon, coffee, peanut butter, and chocolate, and is asked to identify them. In the other test, called the University of Pennsylvania Smell Identification Test (UPSIT), the patient is given 40 scratch-and-sniff samples and four possible answers for each sample. The patient is then asked to match the scratch-and-sniff smell to one of the four suggested answers. These tests help determine the degree of smell loss and whether the patient has anosmia or another type of odor disorder.
If another disease or disorder is causing anosmia, the doctor treats that medical problem, and in some cases the sense of smell returns. For example, if polyps are blocking airflow into the nose, they can be removed surgically. Sometimes, however, damage to the nerves is permanent, or there is no cure for the underlying condition causing loss of smell (e.g., Parkinson's disease or Alzheimer's disease). In general, treatment of complete anosmia is difficult and often not very successful.
Birnbaum, Molly. Season to Taste: How I Lost My Sense of Smell and Found My Way. New York: Ecco, 2011.
Monell Center. “Anosmia FAQ.” Monell Chemical Senses Center. http://www.monell.org/research/anosmia/anosmia_faq (accessed June 16, 2015).
Anosmia Foundation. Website: http://www.anosmiafoundation.com (accessed June 16, 2015).
* congenital (kon-JEH-nih-tul) means present at birth.
* allergy (AL-uhr-jee) is an immune system–related sensitivity to certain substances; for example, cat dander or the pollen of certain plants, which cause various reactions, such as sneezing, runny nose, wheezing, or swollen, itchy patches on the skin, called hives.
* antihistamines (an-tie-HIS-tuhmeens) are drugs used to combat allergic reactions and relieve itching.
* nasal spray (NA-zal) is a mist that is sprayed into the nose.
* nasal (NA-zal) means of or related to the nose.
* polyps (PAH-lips) are bumps or growths, usually on the lining or surface of a body part (such as the nose or intestine). Their size can range from tiny to large enough to cause pain or obstruction. They may be harmless, but they also may be cancerous.
* endocrine (EN-do-krin) refers to a group of glands, such as the thyroid, adrenal, and pituitary glands, and the hormones they produce. The endocrine glands secrete their hormones into the bloodstream, and the hormones travel to the cells that have receptors for them. Certain hormones have effects on mood and sometimes cause emotional swings.
* Parkinson's disease is a disorder of the nervous system that causes shaking, rigid muscles, slow movements, and poor balance.
* meningitis (meh-nin-JY-tis) is an inflammation of the meninges, the membranes that surround the brain and the spinal cord. Meningitis is most often caused by infection with a virus or a bacterium.
* Alzheimer's disease (ALTS-hymerz) is a condition that leads to gradually worsening loss of mental abilities, including memory, judgment, and abstract thinking, as well as changes in personality.
* CT scans, computed tomography (to-MOG-ra-fee) scans, or CAT (computerized axial tomography) scans, use computers to view structures inside the body