Humans are becoming less sensitive to body odour

Everyone experiences smells in their own unique way — with the same scent either pleasant, too intense or even undetectable to different noses.

But it appears that when it comes to body odour, humans’ sense of sweat may be dwindling somewhat.

That’s because scientists have discovered a mutation in the scent receptor for body odour, making it harder to pick up the smell of a nasty stench.

It’s not just with sweat, however, as even the scent receptors for perfume may be waning in intensity, according to a team of researchers from China.

Scientists have discovered a mutation in the scent receptor for body odour, which makes it harder to pick up the smell of a nasty stench (stock image)

What is anosmia?

Anosmia is the medical name for a condition in which someone suffers a complete or partial loss of their sense of smell.

The most common single cause of the condition – temporary or permanent – is illnesses which affect the nose or sinuses, such as polyps which grow in the airways, fractured bones or cartilage, hay fever or tumours.

It is different to hyposmia, which is a decreased sensitivity to smells.

Around 3.5 million people in the UK are affected by it, along with nearly 10 million in the US. It is surprisingly common and affects between three and five per cent of people.

Head injuries and nervous system diseases like Parkinson’s or Alzheimer’s may also contribute to the condition by damaging nerves in the nose which are responsible for detecting smells.

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They believe newer scent receptors for both sweat and perfume are now less sensitive and that humans and other primates’ sense of smell has degraded over time because of changes in the genes that code for these receptors.

In the new study, led by the Chinese Academy of Sciences, researchers screened the genomes of 1,000 Han Chinese people to find genetic variations linked to how the participants perceived 10 different scents.

Then they repeated the experiment for six odours in an ethnically diverse population of 364 people to confirm their results.

The team identified two new receptors, one that detects a synthetic musk used in fragrances and another for a compound in human underarm odour.

Participants carried different versions of the musk and underarm odour receptor genes, and those genetic variations affected how the person perceived the scents, the researchers said.

They found that people with the ancestral versions (the version shared with other non-human primates) of the scent receptors tended to rate the corresponding odour as more intense.

The findings support the hypothesis that the sensitivity of humans’ and other primates’ sense of smell has degraded over time due to changes in the set of genes that code for our various smell receptors.

In the new study researchers screened the genomes of 1,000 Han Chinese people to find genetic variations linked to how the participants perceived 10 different scents (stock image)

The analysis also identified three links between genes for scent receptors and specific odours that scientists had previously reported in studies involving Caucasian participants.

The new results from East Asian and diverse populations suggest that the genetics underlying the ability to detect odours remains constant across people from different backgrounds, the authors said.

They added: ‘Genome-wide scans identified novel genetic variants associated with odor perception, providing support for the hypothesis that the primate olfactory receptor repertoire has degenerated over time.’

The new study has been published in the journal PLOS Genetics.

SCIENTISTS IDENTIFY THE KEY ENZYME BEHIND THE PUNGENT SMELL OF BODY ODOUR – AND IT COULD LEAD TO A NEW GENERATION OF DEODORANTS

The chemical culprit behind body odour has been identified, scientists reported in 2020.

An enzyme made by bacteria which reside in human armpits has been found to produce the pungent scent we know as BO.

Dubbed the ‘BO enzyme’, it is made by bacteria called Staphylococcus hominis which humans inherited from our now-extinct ancient ancestors.

Researchers from the University of York worked with Unilever and discovered body odour has likely plagued Homo sapiens since we first evolved.

We inherited it from our more primitive predecessors and now the smelly bacteria call our armpits home.

Dr Gordon James, of Unilever, says: ‘This research was a real eye-opener.

‘It was fascinating to discover that a key odour-forming enzyme exists in only a select few armpit bacteria – and evolved there tens of millions of years ago.’

By identifying the specific odorous compound, academics believe they can create deodorants that neutralise the enzyme, eradicating BO.

Dr Michelle Rudden, from the University of York’s Department of Biology, said: ‘Solving the structure of this “BO enzyme” has allowed us to pinpoint the molecular step inside certain bacteria that makes the odour molecules.

‘This is a key advancement in understanding how body odour works, and will enable the development of targeted inhibitors that stop BO production at source without disrupting the armpit microbiome.’

The enzymes produced by the bacteria latch onto odourless compounds made by the body’s apocrine glands.

These are in the skin and produce sweat and open into hair follicles. They are only found under the arm, around the nipple and external genitalia.

Human’s also have eccrine glands which are all over the body and do not open into hair follicles.

While eccrine glands are known to be useful in thermoregulation, little is known about the hairy apocrine glands except that they are smelly and hairy.

Scientists know bacteria live there and this microbiota is essential to their functionality.

The study, published in the journal Scientific Reports, found odourless precursor chemicals secreted from the glands are sliced up by the enzyme.

This transforms the harmless, odour-free chemicals into a thioalcohols, which the researchers describe as ‘most pungent volatiles’ in sweat despite being found only in trace levels.

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This post first appeared on Dailymail.co.uk