Smell and Taste Disorders
Smell and taste problems can have a big
impact on our lives. Because these senses contribute substantially to our
enjoyment of life, our desire to eat, and be social, smell and taste disorders
can be serious. When smell and taste are impaired, life loses some zest. We eat
poorly, socialize less, and as a result, feel worse. Many older people
experience this problem.
Smell and taste also warn us about dangers, such as fire, poisonous fumes,
and spoiled food. Certain jobs require that these senses be accurate-chefs and
firemen rely on taste and smell. One study estimates that more than 200,000
people visit a doctor with smell and taste disorders every year, but many more
cases go unreported.
Loss of the sense of smell may be a sign of sinus disease, growths in the
nasal passages, or, in rare circumstances, brain tumors.
How do smell and taste work?
Smell and taste belong to our chemical sensing system (chemosensation). The
complicated processes of smelling and tasting begin 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.
Olfactory (small nerve) cells are stimulated by the odors around
us-the fragrance from a rose, the smell of bread baking. These nerve cells are
found in a tiny patch of tissue high up in the nose, and they connect directly
to the brain.
Gustatory (taste nerve) cells react to food or drink mixed with saliva
and are clustered in the taste buds of the mouth and throat. Many of the small
bumps that can be seen on the tongue contain taste buds. These surface cells
send taste information to nearby nerve fibers, which send messages to the
The common chemical sense, another chemosensory mechanism, contributes
to our senses of smell and taste. In this system, thousands of free nerve
endings-especially on the moist surfaces of the eyes, nose, mouth, and
throat-identify sensations like the sting of ammonia, the coolness of menthol,
and the "heat" of chili peppers.
We can commonly identify four basic taste sensations:
Certain combinations of these tastes-along with texture, temperature, odor,
and the sensations from the common chemical sense-produce a flavor. It is flavor
that lets us know whether we are eating peanuts or caviar.
Many flavors are recognized mainly through
the sense of smell. If you hold your nose while eating chocolate, for example,
you will have trouble identifying the chocolate flavor, even though you can
distinguish the food's sweetness or bitterness. This is because the familiar
flavor of chocolate is sensed largely by odor. So is the well-known flavor of
coffee. This is why a person who wishes to fully savor a delicious flavor (e.g.,
an expert chef testing his own creation) will exhale through his nose after each
swallow. Taste and smell cells are the only cells in the nervous
system that are replaced when they become old or damaged. Scientists are
examining this phenomenon while studying ways to replace other damaged nerve
What causes smell and taste disorders?
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 in identifying odors.
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
Tobacco smoking is the most concentrated form of pollution that most people
will ever be exposed to. It impairs the ability to identify odors and diminishes
the sense of taste. Quitting smoking improves the smell function.
Radiation therapy patients with cancers of the head and neck later complain
of lost smell and taste. These senses can also be lost in the course of some
diseases of the nervous system.
Patients who have lost their larynx (voice box) commonly complain of poor
ability to smell and taste. Laryngectomy patients can use a special "bypass"
tube to breathe through the nose again. The enhanced airflow through the nose
helps smell and taste sensation to be re-established.
How are smell and taste disorders 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 patient
may also be asked to compare the smells or tastes of different chemicals, or how
the intensities of smells or tastes grow when a chemical concentration is
- Smell. Scientists have developed an easily administered
"scratch-and-sniff" test to evaluate the sense of smell.
- Taste. Patients 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 smell and taste disorders be treated?
Sometimes a certain medication is 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 patients, 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.
What can I do to help myself?
If you experience a smell or taste problem, 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,
pollens, danders, 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 a physician who deals with
diseases of the nose and throat (an otolaryngologist-head and neck surgeon).
Proper diagnosis by a trained professional 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 think you taste you really smell.
Diagnosis may also lead to treatment of an underlying cause for the
disturbance. Many types of smell and taste disorders are reversible. But, if
yours is not, it is important to remember that you are not alone. Thousands of
other patients have faced the same situation.
© 2004 AAO-HNS/AAO-HNSF
Please read our disclaimer. Any information provided on this Web site should not be considered medical advice or a substitute for a consultation with Dr. Hector N. Hernandez or other healthcare professional. If you have a medical problem, contact us for diagnosis and treatment.