Smell and Taste
Smell or taste disorders are relatively common and can have a significant impact on quality of life. The senses of smell and taste allow us to enjoy foods and serve as an early warning system against dangers such as fire, smoke, spoiled foods, chemicals and toxins. Smell and taste disorders, especially in the elderly, have been implicated in weight loss, malnutrition, impaired immunity and worsening of medical conditions.
Many individuals, who complain of problems with taste, actually are experiencing problems with their sense of smell.
Two nerves in the nose are responsible for the sense of smell. The olfactory nerve is located in the upper part of the nose and connects directly to the brain. The olfactory nerve is responsible for the quality of smells such as rose, lemon and grass. The second nerve, the trigeminal nerve, gives one the sensation of odors, warmth, coolness, sharpness and irritation (i.e. ammonia and alcohol).
The sense of taste comes from taste buds located on the tongue and throat. The basic taste sensations are sweet, sour, bitter, and salty. The trigeminal nerve also provides the sensation of foods such as stinging, burning, coolness and sharpness.
Causes of Smell and Taste Disorders
Common causes for smell disturbance are nasal and sinus disease (allergies, polyps, sinusitis and enlarged adenoids), upper respiratory infections (“colds”), head trauma (skull and nasal fractures) and cigarette smoking. Less common causes are medications, cocaine use, toxic chemicals (benzene, chlorine, paint
solvents, insecticides) and industrial agents (ashes, chromium, iron). Uncommon causes include tumors, psychiatric conditions (schizophrenia, depression) and endocrine disorders.
Common causes for taste disturbance include mouth infections (yeast, herpes, gum disease), medications, oral appliances (dentures), dental procedures (tooth extraction, root canal) and age. Less common causes are nutritional deficiencies (Zinc, Copper, B3 and B12), malnutrition, kidney and liver disease, cancer and HIV, tumors, head trauma, and toxic chemical exposure (benzene, chlorine, sulfuric acid). Uncommon causes include psychiatric conditions (depression, anorexia, bulimia), epilepsy, migraine headaches, multiple sclerosis, diabetes, hypothyroidism and Sjogren’s syndrome.
Evaluation for Smell and Taste Disorders
A physical examination may detect the cause for a taste or smell disorder. The nose and mouth is examined to look for evidence of infections, inflammations or other disorders. Tests to detect loss of smell include a “scratch-and-sniff” test. Laboratory and imaging studies such as a CT scan or MRI may be ordered to detect abnormalities of the nose, sinuses, mouth, brain and nervous system.
Treatments for Smell and Taste Disorders
Smell disorders may be successfully treated if there is blockage of the nasal passages from polyps, allergies or infections. Medications such as nasal sprays, decongestants and oral steroids may be helpful in improving the sense of smell. Improvement may be noted if one stops certain medications that are affecting one’s sense of smell or taste.
Quitting cigarette smoking will often lead to improvement in the sense of smell and taste. In general, if loss of smell is caused by head injury, the prognosis for recovery is poor. Most individuals that regain their sense of smell after head trauma do so within 12 weeks of injury.
Individuals with permanent loss of smell need to be aware of issues of personal hygiene (body odor), safety (smoke alarms, spoiled food), health and appetite. Improving the appearance and flavor of food with salt, spice, texture, temperature and color, is helpful in making eating more enjoyable.