Colds and flu

Updated 18 April 2016

Why you lose your sense of smell and taste when you’ve got a cold

Colds and flu can strike at any time, but with autumn in the air, your chances of getting one of these viral infections might increase. Take colds, for instance, which are the most common viral infections of the nose and throat.

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There are nearly 100 rhinoviruses that cause more than half of colds, says Dr Marvin Hsiao, medical virologist at the University of Cape Town’s Department of Clinical Laboratory Sciences. He remarks that typical signs of a cold include nasal stuffiness, sore throat, sneezing, headache, cough and mild body aches.

Now count yourself lucky if you only have a cold and not flu, which is far worse and can make you feel as if you need to have your coffin measurements taken.
“Severe flu symptoms (like high fever, weakness, fatigue, body aches and headache) often last five to seven days, while the worst of a cold is usually gone in two to four days,” comments Dr Hsiao.

Read: Why there's no cure for the common cold

Still, what sucks with both colds and flu (aside from feeling ghastly) is that you can’t even enjoy the flavour of that yummy chicken soup you thought would make you feel better. Of course, it’s because you’ve lost your sense of taste along with your sense of humour.  But ever wondered why you can’t taste properly with a cold or stuffy nose?

First question that needs answering is why a cold causes a stuffy nose in the first place.
Dr Hsiao explains that ‘white blood cells in your body produce chemicals to kill virus-infected cells. This causes increased mucous secretions as well as nasal swelling and inflammation.’

Link between smell and taste

More importantly though, is to understand that the flavour of food involves both smell and taste. In fact, 80% of our taste is related to smell, so it’s not surprising that most of the flavour of a food comes from your ability to smell it, explains Professor Jeremiah Alt, Assistant Professor of Surgery and Rhinology at University of Utah Hospitals and Clinics.

In an online article on the American Rhinologic Society (ARS) website, he explains that the tongue is your taste organ, as it can sense salty, sweet, sour, bitter and umami (savoury). “Our sense of smell (known as olfaction) provides the rest of a food’s flavour, which is why it’s difficult to appreciate food flavour when you have nasal obstruction from a cold, stuffy nose or rhinosinusitus.”

Read: Winter is on its way, bringing along colds and flu

Professor Alt points out that a small area called the olfactory cleft high up in the roof of your nose senses smell. Here, special cells sense different odours found in the air that we breathe and then send signals to the brain via the olfactory nerve. Anything that interrupts taste sensations being transmitted to the brain will cause taste problems.

When you have a cold, the swelling causes inflammation and obstruction, which impairs your smell. The flavour of food is produced only after taste is combined with a smell, so if a stuffy nose impairs your sense of smell, it will also decrease your perception of taste.

When your nose is stuffy, taste receptors in your taste buds have to do the job of assessing food flavour in different taste molecules all on their own. Truth is, even though you have around 2000 and 5000 taste buds on your tongue, in your mouth and throat (with each containing 50 to 100 taste receptor cells) they still don’t come close to what your nose knows!

Read: Is it true that you should feed a cold and starve a fever?

The two smell (olfactory) receptors found high up in your nasal passages have up to six million cells and can sniff out differences of at least one trillion odours, according to neurobiologist and olfaction expert Dr Leslie Vosshall, Head of the Laboratory of Neurogenetics and Behavior at The Rockefeller University in New York. 

We know that losing your sense of taste when you have a cold can make you feel miserable, but don’t worry, it usually doesn’t last long. Dr Hsiao gives the reassurance that ‘your normal taste should return when the infection passes.’

When to worry about taste or smell loss

Some people might however, experience a more prolonged or permanent loss of smell after a cold, comments Professor Alt. He says it’s believed this permanent loss happens because of direct injury and inflammation of the olfactory nerve cells (neurons), which in turn, result from the rhinoviruses that cause the cold.

Make an appointment to see your GP if:

- Your taste problems don’t go away

- You experience abnormal taste with other symptoms, see your doctor

- Are worried about a persistent change in your sense of taste or smell

- There is a sudden or unexplained loss of sense of taste or smell.

Read more:

What are colds? 

Causes of a cold 

Treating a cold

Sources:

http://www.livescience.com/44240-human-nose-distinguishes-1-trillion-scents.htmlhttp://patient.info/health/smell-and-taste-disorders

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0072592/

https://www.nlm.nih.gov/medlineplus/ency/article/003050.htm

http://care.american-rhinologic.org/disorders_of_smell_taste?print

http://www.sirc.org/publik/smell_human.html













 

Ask the Expert

Flu expert

Dr Heidi van Deventer completed her MBChB (Bachelor of Medicine and Bachelor of Surgery) degree in 2004 at the University of Stellenbosch.
She has additional training in ACLS (Advanced Cardiac Life Support) and PALS (Paediatric Advanced Life Support) as well as biostatistics and epidemiology.

Dr Van Deventer is currently working as a researcher at the Desmond Tutu Tuberculosis Centre at the University of Stellenbosch.

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