Linked closely with the sense of taste, your sense of smell often gets taken for granted. In general, a quarter of the population have a poor sense of taste, half have an average or normal sense of taste, and a quarter are considered “super” tasters.
Our ability to smell mirrors this distribution, although one to two per cent of people have no sense of smell at all, a condition called anosmia. Often, too, the senses of taste and smell are individual, meaning that what you taste and smell is not the same as another person tastes or smells in response to the same stimulus.
Interestingly, women in general have keener senses of smell than do men.
When you inhale, olfactory sensory neurons at the rear of your nose detect vapourized molecules. Depending upon which receptors are activated, messages are sent to your brain, which then interprets the odour as the scent of roses or dirty sneakers.
However, the roof of your mouth also has olfactory receptors that sense molecules released from the food that you chew, and again your brain distinguishes the smell and taste of the food. Genetically there are as many as 1,000 different types of smell receptors, and humans can identify over 10,000 different smells.
Any condition that causes nasal congestion, for example the common cold, influenza or hay fever, will have an impact on your sense of smell. Ironically, medications applied to the nasal passages will also impair the activity of olfactory receptors, for example decongestant and corticosteroid nasal sprays, which are the very things used to treat nasal congestion!
Saline nasal sprays, nasal moisturizing gels, and nasal douches don’t seem to have the same effect on your ability to smell.
Some drugs can also cause changes in olfactory sensing. The “triptan” drugs used to treat migraine headaches are examples, and in fact some of these drugs are administered by nasal spray. The cardiovascular drug amiodarone; high blood pressure angiotensin converting enzyme or ACE inhibitors such as ramipril, enalapril, lisinopril; and some antibiotics like ciprofloxacin can alter not only smell but taste as well. Often, this adverse reaction is not considered important and people tolerate it.
Diseases that affect the nervous system also affect your ability to smell. Alzheimer’s disease, Parkinson’s disease, and schizophrenia are associated with a reduced sense of smell. As you age, you lose some of both your ability to smell and to taste, and it is thought this is due to a reduction in the number of receptors (our body does have the ability to replace olfactory neuron receptors, but the numbers may just not be sufficient).
Smoking certainly causes damage to olfactory receptors, and once you quit you may be surprised at how tasty food becomes. Unfortunately, for some former smokers, this may mean you eat more and gain weight!
Hormonal disturbances, for example pregnancy, can alter smell receptors making familiar odours unbearable, and any nasal growth or dental problem can impair smell as well as taste. Exposure to chemicals or even air pollution can damage receptors and your sense of smell, so it is important to wear the appropriate mask and other protection when dealing with any potentially harmful substance that you may inhale.
Your sense of smell is important. Smell helps identify potential harm such as fire, gas leaks, and rotten food. Aromatherapy uses the sense of smell to treat psychological and physical conditions, and scents such as air fresheners, are even used to improve productivity and well being at home, work and school.
Memory is deeply affected by smell and in studies, 65 per cent of people can remember a specific smell a year after exposure. For example, it may just take a whiff of baking bread, baby powder, or perfume to remember your mother’s kitchen, your child, or even your aunt and her favourite perfume.