Smell and Taste Disorders
If you are experiencing a problem with the ability to smell or taste, you are not alone. Over 200,000 people visit a physician for this type of problem and there are many who never seek medical attention.
Many people complain of a decrease in both smell and taste, however in most cases the problem is related to a smell loss only. Strictly speaking, taste specifically refers to the ability of the tongue to detect sweet, salt, bitter, and sour. However, flavor combines taste with texture, color, temperature, and especially smell to provide us the experience we normally enjoy when eating. So, our ability to tell the difference between chocolate and strawberry ice cream is difficult with a loss of smell, but the sweet taste remains.
Our sense of smell begins when an odor enters the nose and reaches the special smell (olfactory) nerves in the roof of the nasal cavity. The nerves then send signals to the brain where we recognize a smell. These nerves can be damaged, but luckily as in all animals, these nerves can be replaced with new ones. When there is an interruption in the ability of an odorant to travel from the outside to inside the nose and from the inside of the nose to the smell nerves of the nasal cavity and from the smell nerves to the brain, a smell disorder occurs. We call a decreased sense of smell hyposmia, and a total loss of smell anosmia. Phantosmia is the term given when someone thinks they can smell something when no one else in the room smells the same thing. This can occasionally indicate an infection.
Disorders of the sense of smell can occur for many different reasons. Medications, metabolic disorders, and nutritional deficiencies are some examples. However, the three most common reasons for smell disorders include head injury, upper respiratory tract infection, and nasal obstruction due to sinus disease and polyps. Head injury may result in an immediate smell loss. Some people in this group will regain their sense of smell, but some have a permanent loss. A smell loss after a cold is also immediate with persistence of the smell loss after resolution of the other infection symptoms. Again, a proportion of these people will regain the ability to smell, but others will have a permanent loss. Smell loss due to nasal obstruction usually in the form of nasal and sinus polyps usually occurs gradually and will come and go, often in relation to an increase in sinusitis symptoms.
We experience taste when a substance contacts one of four taste receptor cells for sweet, salt, bitter, or sour. The receptor cells are located in taste buds spread over the surface of the tongue and throat. Three different nerves allow us to taste, therefore it is very difficult to lose all sense of taste through a nerve injury. In addition, like the smell nerves, the taste receptor cells are replaceable and if damaged they can grow back. A decrease in ability to taste is called hypogeusia, and a total loss of taste is termed ageusia. Taste disorders like smell disorders can occur for many different reasons. Total loss of taste often indicates a disorder throughout the body such as due to toxicity, medications, or nutrition disorders. Decreased or abnormal taste can also occur from poor dentition or from cancer of the mouth.
Besides a detailed history and head and neck exam, evaluation by an otolaryngologist for smell and taste disorders may include smell and taste testing. Testing of smell function often includes taking a “scratch and sniff” odor identification test matching a smell with a list of odors. Taste function can be tested by applying four different solutions (sweet, salt, bitter, and sour) to four different regions of the tongue. Additional evaluation may include a CT scan and/or an MRI of the brain and sinuses.
With a loss of smell, there is a decreased ability to smell smoke, natural gas, and spoiled food. It’s important for a person with these disorders to have proper smoke detectors. (Click for information on What You Need to Know About Natural Gas Detectors). Switching from natural gas to electrical appliances adds even more safety and natural gas detectors are also available to warn of any leaks. In general, disorders of smell and taste may indicate a significant medical condition and therefore requires detailed head and neck evaluation from an otolaryngologist.