Problems with the senses, smell and taste, have substantial impact on our lives. These senses are the reason we enjoy life and have appetite to eat and maintain decent social relations. If our smell and taste senses become impaired, life might not make sense anymore. If we don’t taste the food, we eat less. Our social life eventually starts to decline if we cannot perceive the smell and taste of our choice of food. Smell and taste impairments are seen more commonly in older ages.
How do smell and taste work?
There are chemical sensory receptors in the nose and mouth, which enable smelling and tasting. These receptors are stimulated by the molecules of the substances that touch our nose and mouth. Extensions of the receptors to the brain, which are nerves, transmit signals coming from different molecules to the special sections of the brain that are reserved for smell and taste, by acting like power extension cords. On the account of their recognition, smelling and tasting is achieved. These two senses operate in coordination. The smelling nerve fibers come from the brain and directly extend its tips to the upper areas of nasal fossae. The receptors on these nerve tips are stimulated various odors around us. They are stimulated by fragrant scents (flowers, perfumes, soaps), or bad odors (petroleum, gas, cigarette) around us. Tasting receptors are found inside the mouth and throat and particularly on the tongue. When we examine the surface of the tongue carefully, we discern tiny wart-like bumps, which are actually taste receptors of the tongue. When the food or drink start the digestion in our mouth by saliva interaction, the scattered receptors on the tongue receive stimuli with the contact and they transmit them to the brain via nerve fibers. In general, we can distinguish four main flavors; sour, sweet, salty and bitter. When the blend of these tastes mixes with the content, texture, warmth and flavor, it created a taste that can be distinguished by the chemical receptors. By means of this process, we can identify taste of a kebab or a fruit. Many tastes are also recognized by our sense of smell. So, for example, when eating a meal with garlic, if you shut your nostrils or if you are eating that meal while you are with flu, you can tell whether the food is sweet or sour. Yet, you might not get the taste of garlic. This is because the sensorial evaluation of garlic is achieved mainly by smell receptors. Scientific researches suggest that, smell and taste nerve cells that are aged or damaged due to aging, are repaired by nervous system. Whereas, other nerve cells or receptors in the nervous system have no capacity to renew themselves. The sense of smell is most accurate between the ages 30-60 years. But it begins to decline after age 60. Majority of elderly people gradually lose their smelling ability because of aging. They complain of either total incapability of smelling or partially inadequate sense of smell. Usually, women are more accurate than men in distinguishing odors. Some people are born with a poor sense of smell or taste. Unfortunately, congenital smell disorders have no effective remedy today. Upper respiratory tract infections may, in some cases, temporarily or permanently, impair the ability of intranasal receptors to perceive odors. Even if the molecules in the air reach into the nasal cavity, paralyzed smelling receptors cannot convey the stimuli to the brain. So smelling sense cannot occur. Cranial traumas, in some cases, might also paralyze sensorial pathways of smelling and tasting temporarily or permanently. Subsequently such traumas may result in sensorial disorders. Even though the nerves and nerve endings in the nose are fully sound and undamaged, polyps inside the nose that would impede the meeting of molecules and nerve ending receptors aptly, nasal polyps or nasal edema causing sinusitis that might cause smelling and tasting impairments. Hormonal disorders, dental and gingival problems, oral wounds or poor oral hygiene might have negative effect on the senses of taste and smell. Prolonged exposure to certain chemicals may permanently erode smell and taste cells, so this condition might result in bluntness in smelling and tasting ability. For active or passive smokers, impairement in ability to distinguish smells also cause decline in their sense of taste. By increasing the swelling inside the nose, cigarette toughens the scent molecules’ arrival at the target, which would stimulate the receptors. Futhermore, nicotine’s direct contact with smell and taste receptors would cause smell and taste diorder, change and decline. This disorder most probably will recover when smoking is discontinued. Receiving radiotherapy treatment for head and neck cancers might cause decline or disorder in senses of smell and taste. Also some nervous system diseases (Parkinson, Alzheimer) might be the cause of such disorder.
How could we notice the decline in tasting and smelling?
An easily administered test has been developed to evaluate the level of sensory loss, in which the patients are asked to sniff a series of paper slips in a booklet in order to identify each odor specifically and the responses are noted and analyzed. In the tasting test, it is determined that the four main flavors in various intensities are applied to the particular sites of the tongue to taste.
If the substantial underlying cause is a drug applied, immediately after its discontinuation, the complaints relieve. Generally, anti allergic drugs can rehabilitate the sense of smell and taste disorders. Some patients suffer from smell and taste disorder especially due to prolonged upper respiratory tract infections or seasonal allergies but when their condition improves the disorder fades away on its own. Whereas in most cases, when the nasal polys and swelling, which impair the transmission between the molecules and the nerve ending receptors, is fixed, the smell and taste disorder straightens, since the connection between the molecules and the nerve ending receptors is instituted uninterruptedly. These two chemical senses might perish in time on their own but they might as well improve and return to their normal natures. If someone notices a slight disorder in the smell or taste ability, they should see a physician, preferably an ENT expert. Certain information, such as, whether this problem started by a simple flu or a strike to the head or due to the surrounding conditions and if it is related to nasal congestion or not, will help you and your doctor to solve the problem. And also, knowing if that disorder improves occasionally or not and if it shows seasonal changes or not, will help us to handle seasonal allergy problem accordingly. Your ENT specialist will examine you in detail and if needed will perform smell and taste tests. Physician may further ask for computerized tomography (CT) or magnetic resonance imaging (MRI) viewingas well. Based on the results of these tests sometimes simple medical treatments would suffice to solve the problems.