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Smell & Taste

Insight into Important Senses

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Problems with these senses have a big impact on our lives. Smell and taste contribute to our enjoyment of life by stimulating a desire to eat – which not only nourishes our bodies but also enhances our social activities. When smell and taste become impaired, we eat poorly, socialize less, and feel worse. Smell and taste warn us of dangers, such as fire, poisonous fumes, and spoiled food. Loss of the sense of smell may indicate sinus disease, growths in the nasal passages, or, at times, brain tumors.

How do smell and taste work?
Smell and taste belong to our chemical sensing system (chemosensation). The complicated process of smelling and tasting begins when molecules released by the substances around us stimulate special nerve cells in the nose, mouth, or throat. These cells transmit messages to the brain, where specific smells or tastes are identified.

What causes loss of smell and taste?
Scientists have found that the sense of smell is most accurate between the ages of 30 and 60 years. It begins to decline after age 60, and a large proportion of elderly persons lose their smelling ability. Women of all ages are generally more accurate than men are in identifying odors.

Some people, notably those with serious respiratory infections or seasonal allergies, regain their smell or taste simply by waiting for their illness to run its course.

Some people are born with a poor sense of smell or taste. Upper respiratory infections are blamed for some losses, and injury to the head can also cause smell or taste problems. Loss of smell and taste may result from polyps in the nasal or sinus cavities, hormonal disturbances, or dental problems. They can also be caused by prolonged exposure to certain chemicals, such as insecticides, and by some medicines. Tobacco smoking is the most concentrated form of pollution to which most people are exposed. It impairs the ability to identify odors and diminishes the sense of taste. Quitting smoking improves the smell function.

People undergoing radiation therapy for cancers of the head and neck often complain of lost smell and taste. These senses can also be lost in the course of some diseases of the nervous system. People who have lost their larynx commonly complain of poor ability to smell and taste.

How are smell and taste loss diagnosed?
The extent of loss of smell or taste can be tested using the lowest concentration of a chemical that a person can detect and recognize. A person may also be asked to compare the smells or tastes of different chemicals and identify how the intensities of smells and tastes grow when a chemical concentration is increased. Scientists have developed an easily administered “scratch-and-sniff” test to evaluate the sense of smell. People react to different chemical concentrations in taste testing; this may involve a simple “sip, spit, and rinse” test, or chemicals may be applied directly to specific areas of the tongue.

Can these disorders be treated?
Sometimes, certain medications are the cause of smell or taste disorders, and improvement occurs when that medicine is stopped or changed. Although certain medications can cause chemosensory problems, others – particularly anti-allergy drugs – seem to improve the senses of taste and smell. Some people, notably those with serious respiratory infections or seasonal allergies, regain their smell or taste simply by waiting for their illness to run its course. In many cases, nasal obstructions, such as polyps, can be removed to restore airflow to the receptor area and can correct the loss of smell and taste. Occasionally, chemosenses return to normal just as spontaneously as they disappeared.

How do you cope with smell or taste problems?
If you experience problems in smelling or tasting, try to identify and record the circumstances surrounding it. When did you first become aware of it? Did you have a cold or flu then? A head injury? Were you exposed to air pollutants or pollens, dander, or dust to which you might be allergic? Is this a recurring problem? Does it come in any special season, like hay fever time?

Bring all this information with you when you visit your doctor. Proper diagnosis can provide reassurance that your illness is not imaginary. You may even be surprised by the results. For example, what you may think is a taste problem could actually be a smell problem because much of what you taste is really caused by smell.

Diagnosis may also lead to treatment of an underlying cause for the disturbance. Remember, many types of smell and taste disorders are reversible.

 

Source: American Academy of Otolaryngology – Head and Neck Surgery, www.aaoaf.org

This article was originally published in Coping® with Allergies & Asthma magazine, September/October 2009.