What causes loss of taste and smell
Clinical Overview or FYI. Often, it can be difficult to obtain information regarding taste and smell dysfunctions. Here are a few facts which may help you understand more about these problems.
INCIDENCE: Taste and smell problems are common. Although estimates vary, our surveys indicate that about 7% of the people in the United States (about 21 million people) suffer from chronic dysfunction of smell or taste.
SYMPTOMS: There are two major types of problems related to taste and smell: (1) loss of function and (2) distortion of function. Loss of function means that you cannot taste or smell as well as you could before your loss. Many patients feel they cannot taste but they mean they cannot get flavor out of food which relates more to smell loss than taste loss. Distortion of function means that foods or odors that normally are pleasant may taste or smell odd or distorted, perhaps with an unpleasant chemical or a rotten taste or smell. You may experience a taste in your mouth without the presence of any food or drink or an odor in your nose without any vapor in the environment; this can be quite confusing and you may wonder if this is real or just your imagination. These phenomena are quite real and reflect several aspects of what is generally known as dysgeusia and dysosmia. Some patients feel that the taste in their mouth can be noticed by others and feel they have bad breath or halitosis, whereas others may feel that they emit an unpleasant odor from their body. Some patients do not have a taste or smell problem but have a burning (pyrosis) on their tongue or in their mouth. These symptoms can be intermittent or persistent, they may wax and wane in strength and they may get worse at some periods of the day or night or with fatigue or stress.
CAUSES: Each of these symptoms can relate to several causes. Most frequently symptoms follow an influenza-like illness but they also can follow a head injury, an acute or chronic attack of allergies or for reasons that may not be immediately apparent. Some drugs taken to treat diseases you may have can cause these symptoms.
MEDICAL ASSISTANCE: Many of you may have gone to your local doctor or to medical specialists who may have examined you and found no specific pathology. You may have had X-rays, CT scans, or MRIs which did not show any problem. You may have been told that there was nothing wrong with you and that if you wait the symptoms will disappear. You may have also been told that there was nothing medically that could be done for you. Since most physicians are unfamiliar with these problems these responses are not uncommon.
PATHOLOGY: It is important for you to know that these problems are commonly due to a disease process. There are three major parts of the taste and smell systems which can be affected by disease, the brain, the nerves and the receptors. By far the parts that are affected most commonly by disease are the taste and smell receptors, organs which receive information about taste and smell before it reaches the nerves or the brain. These receptors are
located in your taste buds in your mouth for taste and in your olfactory epithelium, high up in your nose, for smell. These receptors normally grow, develop and die over a period of 1-7 days and are nourished by specialized substances (proteins) secreted in saliva from your parotid gland in your mouth (for taste) and in nasal mucus from serous glands in your nose (for smell). The illnesses or injuries which caused your symptoms commonly decrease the secretion of these nourishing substances thereby decreasing growth, development and producing dysfunction of these receptors, This would be similar to a pathological process decreasing secretion of some substance in your blood which produced a disease; e.g. decreased insulin secretion causing diabetes or decreased thyroid hormone secretion causing hypothyroidism. These pathological changes in your receptors are the most common cause of your symptoms.
DIAGNOSIS: In order to understand the cause of your dysfunction it is important to obtain a careful history of your complaints and an examination of your head and neck. While some patients may exhibit anatomical abnormalities in their nose which may relate to nasal allergies, and these abnormalities are important to investigate, these abnormalities themselves do not usually cause severe smell or taste loss. Specific quantitative measurements of your taste and smell function need to be performed. Protein growth factors in your saliva must be measured in an specific manner to test their function as do tests of substances in your blood and urine which can also indicate causes of your dysfunction. Radiographic and magnetic resonance imaging studies may need to be performed as do other specialized tests. At present, some of these tests can be performed only at The Taste and Smell Clinic, Washington, D. C. and the results of these tests are critical to determine the course of your treatment.
TREATMENT: Although causes vary and treatment depends upon cause, in a large number of patients increasing the secretion of these nourishing substances can correct your symptoms by increasing the growth and development of these impaired receptors and improving their function. In other patients, direct treatment of the receptor malfunction itself may be necessary to correct the symptoms. Treatment usually consists of a medication to be taken orally which can help increase production of these proteins from the parotid gland and/or the nasal serous glands and thereby correct the receptor malfunction.
OUTCOMES: Most patients can be treated effectively after a specific set of biochemical tests are performed which can identify the problem and establish a clinical diagnosis. Treatment corrects the receptor malfunction causing the symptoms of loss and/or distortion of taste and smell function to diminish or disappear, However, this treatment may require weeks or months in order to increase protein secretion and correct the symptoms. This prolonged period can be discouraging to you. Nevertheless progress can be made, albeit slowly, and with patience, your symptoms can be corrected provided the problem which caused your symptoms can be identified and then treated.
The descriptions on this site are for informational purposes only and are not intended to substitute for professional medical diagnosis and/or treatment.
If you have further questions, please contact the Taste and Smell Clinic directly.
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