Smell and taste are strong sensations shared by animals and humans. We all know how is the sting of ammonia, the coolness of menthol, and the “heat” of chili peppers. We know how a chocolate tastes and coffee smells. We can detect substances with eyes closed just because we can smell or taste them.
Importance of smell and taste
Smell and taste are both sensations. The two are closely linked. Anything that tastes good should also smell good to be consumed as food. This is where the two sensations show a close interplay. Taste helps to decide whether or not to consume a food item. Smell plays an important role in animals for recognizing territories, mating, and forming social groups. Smell helps to detect safer environments as the bad smelling ones are potentially dangerous. Smell and taste together are a type of chemosensation, i.e. they help to help to sense the chemicals in food and environment.
Difference between taste and flavor
Taste and flavor are different though the terms are used interchangeably when referring to food. Taste is actually a component of flavor. Flavor is a complex mix of sensory inputs like taste, smell, and chewing. Taste is described as sour, sweet, bitter, and salty. These are the sensations that the tongue can detect as it has separate buds to detect each of these tastes. Flavor is usually identified by the sense of smell. The flavor of coffee or chocolate is better appreciated in smell than taste. Flavor is thus, an amalgamation of smell, taste, texture, and temperature of food.
Problems with ability to smell or taste
Sensation of smell and taste may decline with age. Some children may be deficient for the sensation of smell since birth. Smell and taste may be lost due to damage to the nerves carrying these sensations to the brain that perceives them. Both these can be altered due to side effects of certain medicines. For example, alcohol, nicotine, and zinc salts and certain inhaled medicines can change the sensation of smell. Bad taste, also called dysgusia, can be produced by medicines like metronidazole. Cancers of the head and neck, like those of the mouth or oral cavity, or of sinuses or nasal region can cause loss of taste or smell. Similar effects are also seen after radiotherapy used in treatment of other cancers of the region. Some endocrine disorders related to the hormonal systems in the body like diabetes and hypothyroidism can compromise these sensations. Smell can be lost due to inflammation of the nose called rhinitis or due to masses that block the nasal cavities. One such mass that causes obstruction is a polyp that is an outgrowth of the lining of the nasal cavity that blocks the lumen and hence the sensation of smell. Head trauma, brain surgery, and degenerative disorders like Parkinson’s or Alzheimer’s disease can cause loss of these sensations. Taste can be lost due to poor oral hygiene, infections in the mouth, use of dentures, vigorous tongue brushing, and in general disorders of the body like liver or kidney failure.
Complications
Smell and taste are vital sensations and loss of either or both can be serious. The sense of smell helps to predict dangers like smoke, spoiled food, and hazardous fumes. A change in smelling ability can lead to change in eating habits and food may no longer be enjoyable. Taste helps to prevent the consumption of unhealthy food, and is more important in food allergies where the harmful food item can be recognized by taste. The loss of these sensations can lead to depression and anxiety.
Diagnosis
The first step towards the diagnosis of disorders of smell or taste is a proper history of complaints, and a complete examination to rule out any underlying disorders. The extent of loss of these sensations can be measured by using chemicals in lowest concentrations that can be recognized or detected. A comparison of different tastes or smells enables confirmation of the loss. For smell, the “scratch-and-sniff” test is used. A booklet of sheets containing tiny beads is used and the patient needs to scratch and recognize the odor. To test for taste, chemicals may be applied to specific areas on the tongue, like the tip, rear, or sides to know if the same can be sensed. Alternatively, the patient may be required to sip different substances to taste them. This is called the “sip, spit, and rinse” test. In addition, specific tests may be done for the other conditions like a blood glucose test for diabetes, and hormone levels in blood in the thyroid disorders. CT scans or MRI of the head and neck may be done to detect any suspected local problems.
Treatment
The treatment of altered sensation of taste or smell primarily depends upon the treatment of the underlying disorders, if any. If any medicines are believed to cause the alteration, the same should be discontinued. Any local inflammations and infections should be treated. Any obstructions like polyps should be treated.
Outlook
Generally, the loss of taste or smell can be reversed by addressing the underlying cause. It is most important to never ignore any complaints about smell or taste. These could be suggestive of an underlying medical problem. A timely diagnosis is important to bring back these sensations when lost. Smell and taste are incredible sensations. It makes sense to care for them and safeguard them.
