Taste and smell belong to our chemical sensing system
The complicated process of smelling and tasting begins when molecules released by the substances around us stimulate special nerve cells in the nose, mouth, or throat
These cells transmit messages to the brain, where specific smells or tastes are identified
Our body’s ability to sense chemicals is another chemosensory mechanism that contributes to our senses of smell and taste
In this system, thousands of free nerve endings—especially on the moist surfaces of the eyes, nose, mouth, and throat
Taste and smell allows us to identify sensations like the sting of ammonia, the coolness of menthol, and the “heat” of chili peppers
The sense of smell
Olfactory (smell nerve) cells are stimulated by the odours around us, for example. the fragrance from a rose, the smell of bread baking
These nerve cells are found in a tiny patch of tissue high up in the nose, and they connect directly to the brain
The sense of taste
Gustatory (taste nerve) cells are clustered in the taste buds of the mouth and throat
They react to food or drink mixed with saliva
Many of the small bumps that can be seen on the tongue contain taste buds
These surface cells send taste information to nearby nerve fibres, which send messages to the brain
What causes loss of taste and smell?
Aging
Scientists have found that the sense of smell is most accurate between the ages of 30 and 60 years
It begins to decline after age 60, and a large proportion of elderly persons lose their smelling ability
Gender
Women of all ages are generally more accurate than men in identifying odours
Genetics
Some people are born with a poor sense of taste and smell
Cold and flu
Upper respiratory infections are blamed for some losses, and injury to the head can also cause taste and smell problems
Chronic sinusitis and nasal polyps
Loss of taste and smell may result from polyps in the nasal or sinus cavities
Irritants and chemicals
Loss of taste and smell can also be caused by prolonged exposure to certain chemicals such as insecticides, and by some medicines
Tobacco smoking is the most concentrated form of pollution that most people are exposed to – it impairs the ability to identify odours and diminishes the sense of taste
Quitting smoking improves the taste and smell function
Head and neck causes
Radiation therapy patients with cancers of the head and neck often report loss of smell and taste – these senses can also be lost in the course of some diseases of the nervous system
Patients who have lost their larynx (voice box) commonly report poor ability to smell and taste
Laryngectomy patients can use a special “bypass” tube to breathe through the nose again – the enhanced air flow through the nose helps smell and taste sensations to be re-established
How are loss of taste and smell diagnosed?
The extent of loss of smell or taste can be tested using the lowest concentration of a chemical that a person can detect and recognize
A patient may also be asked to compare the smells or tastes of different chemicals, and how the intensities of smells and tastes grow when a chemical concentration is increased
Smell — Scientists have developed an easily administered “scratch-and-sniff” test to evaluate the sense of smell
Taste — Patients react to different chemical concentrations in taste testing; this may involve a simple “sip, spit, and rinse” test, or chemicals may be applied directly to specific areas of the tongue
Can these disorders be treated?
Sometimes certain medications are the cause of smell or taste disorders, and improvement occurs when that medicine is stopped or changed
Although certain medications can cause chemosensory problems, others—particularly anti-allergy drugs—seem to improve the senses of taste and smell
Some patients, notably those with serious respiratory infections or seasonal allergies, regain their smell or taste simply by waiting for their illness to run its course
In many cases, nasal obstructions, such as polyps, can be removed to restore airflow to the receptor area and can correct the loss of smell and taste
Occasionally, the sense of taste and smell return to normal just as spontaneously as they disappeared
How do you cope with taste and smell problems?
If you experience problems in smelling or tasting, try to identify and record the circumstances surrounding it:
When did you first become aware of it?
Did you have a cold or flu then?
A head injury?
Were you exposed to air pollutants, pollens, danders, or dust to which you might be allergic?
Is this a recurring problem?
Does it come in any special season, like hayfever time?
Management of smell and taste problems
Bring the details regarding your symptoms with you when you visit an ENT specialist who deals with diseases of the nose and throat (an otolaryngologist—head and neck surgeon)
Proper diagnosis by an experienced ENT specialist can provide reassurance that your illness is not imaginary
You may even be surprised by the results
For example, what you may think is a taste problem could actually be a smell problem, because much of what you taste is really caused by smell
Diagnosis may also lead to treatment of an underlying cause for the disturbance – remember, many types of smell and taste disorders are reversible.
Flavour
Four commonly identified taste sensations:
sweet
sour
bitter
salt
Certain tastes combine with texture, temperature, and odour to produce a flavour that allows us to identify what we are eating
Many flavours are recognized through the sense of smell
If you hold your nose while eating chocolate, for example, you will have trouble identifying the chocolate flavour, even though you can distinguish the food’s sweetness or bitterness
This is because the familiar flavour of chocolate is sensed largely by odour
So is the well known flavour of coffee
This is why a person who wishes to fully enjoy a delicious flavour (e.g., an expert chef testing his own creation) will exhale through his nose after each swallow
Natural regeneration of taste and smell nerves
Taste and smell cells are the only cells in the nervous system that are replaced when they become old or damaged
Scientists are examining this phenomenon while studying ways to replace other damaged nerve cells
