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The Power of Smell

April 29, 2022   Return

“5% of our DNA is devoted to the sense of smell (olfaction), a fact that emphasises how important it is” –Noam Sobel, scientist.

Dr Azida Zainal Anuar     Consultant ENT & Head and Neck Surgeon

Our nose is responsible for the all-important function of smell, without which it’ll be a dull world.

“Smell is one of the most complex human senses,” says Dr Azida Zainal Anuar, a consultant ENT as well as a head and neck surgeon.

When we’re able to smell what we eat and, our mealtimes become a more pleasurable experience. Furthermore, the sense of smell also alerts us to signs of danger e.g. fire, gas leaks, etc.

The Art of Breathing

When we breathe, we inhale odour molecules that reach the olfactory epithelium high up in our nose. This epithelium contains millions of sensory nerve endings, which have structures called receptors. These receptors bind odour molecules by functioning like locks and keys – they are “lock” and the odor molecules are the “keys” that fit into the “key slot” of the “lock”.

We have 450 types of olfactory receptors and each receptor can be activated by many different odour molecules. When activated, an electrical signal is sent from the sensory nerves to the olfactory bulb at the base of our forebrain. This olfactory bulb sends the information directly to the limbic system within our brain.

“The limbic system governs our emotions. So, when the messages reach the limbic system, our emotions are stimulated. The information is also related to the hippocampus— which governs memory — making us recall previous experiences. Finally, the information goes to the conscious centre of the brain where the smell is interpreted,” says Dr Azida.

Researchers predict that the average person can detect at least 1 trillion different smells. Our nose can actually outperform our eyes and ears!

When we can’t smell…

A lot of mucous is produced in our nose and sinuses every day to keep our airway moist and filter the air we breathe in. When we are healthy, the mucous is moved to the back of the nose by beating cilia and swallowed.

When we’re down with a cold or the flu, the cilia stop beating and, thus, fail to transport the mucous, which then builds up in our nose and sinuses. At the same time, the mucosal lining swells up and blocks up our sinuses. This chain of events affects our sense of smell.

People with allergies also can’t smell because more mucus is produced and it blocks their nose and sinuses. Although most people believe that allergies like allergic rhinitis and sinusitis are caused by environmental allergens (such as dust mites, pet dander, mold and pollen), the root cause is actually the person’s immune system, which has somehow been tuned to ‘hypersensitive mode’, strongly influenced by genetics, says Dr Azida.

“Most people with allergic rhinitis or sinusitis can diagnose the problem themselves simply by recognising typical symptoms. Both allergic rhinitis and sinusitis can cause anosmia or loss of smell due to a blocked nose or an obstructive lesion like a polyp in their nose. In these cases, removal of the obstructive factor may lead to return of the sense of smell. But sometimes, it may not,” says Dr Azida.

Quality of life takes a plunge for allergy sufferers as they are constantly sneezing and having runny or blocked nose. It’s worse when infection sets in – the mucous changes from colourless fluid to greenish pus.

Besides, allergic rhinitis patients also suffer from asthma and sleep apnoea so allergic rhinitis must be treated properly, advises Dr Azida.

Dr Azida says allergic rhinitis can be treated with medications and immunotherapy. Natural therapies are also available. However, it is best for sufferers to avoid allergens in the first place and seek help from medical professionals.

Quick tips on managing allergic rhinitis and sinusitis:

  1. Minimise exposure to allergens by closing windows and running air conditioners.
  2. Reduce exposure to allergens such as dust mites and molds, by covering pillows and mattresses with pillow protectors and removing dust-collecting household items, such as carpets, heavy drapes and bedspreads.
  3. Although air purifiers and dust filters can be costly, they may help reduce the amount of allergens in the air.
  4. Saline nasal sprays and humidifiers can help clear congestion.
  5. Avoid strong smells like perfumes or colognes and flowers that trigger allergic rhinitis and sinusitis


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2. WebMD. Available at

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