Taste and Smell Disorders (Chemosensory Loss)

The senses of taste and smell are so closely related physiologically that a disorder affecting one is likely to have an adverse effect on the other as well. An estimated 80 to 90 percent of the people who think they have lost their sense of taste have actually lost their ability to smell instead.

The sense of smell declines sharply with age; studies show that more than half of Americans aged 65 to 80, and three-fourths of those over 80, have serious problems in detecting or identifying odors. A significant number in both age groups cannot smell at all.

The sense of taste originates in the tongue's taste buds, which can differentiate among sweet, sour, bitter, and salty. When food is chewed and swallowed, its odors make their way from the back of the mouth to the upper nasal cavity where they stimulate specialized olfactory cells that send odor signals to the brain. This information enables a person to distinguish between foods that have the same texture but different flavors. Someone who cannot smell may find that an apple, onion, and peach all taste alike.

Research indicates that the brain's olfactory receptor cells can differentiate among thousands of odors, including pheromones, chemicals in sweat that appear to play an important role in sexual attraction. Still, our sense of smell lags behind that of most animals. For instance, each person emits a unique scent, yet we generally do not recognize each other by odor, your pet, however, can probably recognize you solely by sniffing.

While taste and smell disorders are rarely fatal, loss or distortion of these perceptions diminishes enjoyment of many of life's important pleasures, including the savoring of food. In some instances, these disorders can have dangerous consequences, as may occur when a person does not smell an incipient kitchen fire or recognize the rancid taste of spoiled food.

Some disorders that affect taste and smell, such as the common cold and hay fever, are minor and self-limiting. Prolonged exposure to tobacco smoke and other environmental pollutants and toxic industrial chemicals can cause a gradual loss of smell sense, which is usually reversible if the irritant is removed.

Permanent destruction of the olfactory cells can result from a severe head injury or from radiation treatment for neck or head cancer. The loss of the ability to smell may accompany Alzheimer's or Parkinson's diseases. Tumors of the nose, mouth, or brain can also cause permanently impaired taste and smell.

Diagnostic Studies and Procedures

Diagnosis of taste and smell disorders may require a team effort involving a neurologist, psychologist, and nutritionist, as well as a doctor who specializes in this aspect of otolaryngology. A patient may be given a scratch-and-sniff test to determine whether or not she can identify familiar odors.

To identify the cause, additional procedures may include a careful inspection of the head and neck, including the tongue. Substances may be placed on the patient's tongue to see if he can differentiate among sweet, salty, sour, and bitter tastes. A CT scan may be used to check for anatomical defects or tumors that might affect taste and smell.

Medical Treatments

Treatments depend on the underlying cause of the disorder. Chronic nasal sinus blockage from allergies or the blockage of air flow by nasal polyps may be treated by hydrocortisone injections and/or surgery. Sinus infections will be treated with antibiotics. Surgery may also be recommended to correct a deviated septum or other defect causing nasal congestion and an impaired sense of smell.

Alternative Therapies

Herbal Medicine. Horseradish, cayenne pepper, and other hot herbs arid spices can help clear sinuses and may restore a sense of smell due to nasal congestion. The spices can be sniffed or added to food.

Naturopathy. Some naturopaths attribute loss of taste perception to vitamin and mineral deficiencies; they may recommend supplements of vitamins A and B12, zinc, and copper. However, be sure to consult a doctor before taking high doses of these nutrients.

Nutrition Therapy. A nutritionist can advise an older person who is inadequately nourished because "everything tastes the same" in ways of preparing more appealing and nutritionally balanced meals. Sometimes, using extra spices and herbs -- for example, sage, garlic, cinnamon, nutmeg, and mint -- give foods more flavor, even for those with an impaired sense of smell.

Self-Treatment

If your loss of smell is due to allergies, ask a doctor about medication or allergy shots. If you smoke, make every effort to stop, and avoid secondhand smoke and other irritants.

Pay attention to good dental hygiene; tooth decay and gum disease can leave a bad taste in your mouth and interfere with your ability to taste food
If you live alone and you have an impaired sense of taste and/or smell, label all perishable foods with the date of purchase and discard any for which freshness is in doubt.

Other Causes of Impaired Taste

Advanced cancer can alter taste perception, especially of meat. In addition to the disorders cited earlier, circumstances that can diminish senses of taste and smell include dry mouth, nose deformities, oral thrush, and disorders affecting the tongue.