What causes body odor? - Mel Rosenberg
A pungent blend of onions, cheese,
and cat urine with hints of...
is that…wet goat?
Most of us don’t need more than one whiff
to identify that generally unpleasant,
characteristic smell we call body odor.
But it’s a surprisingly complex phenomenon
influenced by our genetic makeup,
age, diet, and hygiene.
So what is this odor, exactly?
Where does it come from?
And can we do anything about it?
To start, you just need two things
to produce that familiar scent:
your armpit’s own secretions
and the bacteria that feed on them.
Most people associate
body odor with sweat,
and it’s an important piece of the puzzle.
Your body has millions of sweat glands,
and they come in two major types:
eccrine glands are found
all over your skin
and secrete mainly water and salt.
Apocrine glands, on the other hand,
develop at puberty in your armpits
and a few other places on your body.
The sweat they secrete
is full of proteins and fats.
By themselves,
these secretions are usually odorless.
That’s where bacteria come in.
Every square centimeter of our bodies
is covered with thousands of bacteria.
Many microorganisms thrive
in moist environments, like our armpits.
There, you can find about a million
bacteria per square centimeter,
one of the highest concentrations
anywhere on the skin.
Lurking in this throng of microorganisms
are species of Corynebacteria,
Staphylococci,
Micrococci,
and others.
When these bacteria feed on the proteins
and fats in apocrine sweat,
they turn the odorless compounds into
new ones that can smell very unpleasant.
Some of the worst offenders may be
sulfur-containing chemicals;
those give body odor its oniony aroma.
Carboxylic acids are in the mix, too,
adding notes of cheese.
These molecules waft up from the armpit
and can be sucked directly into our noses,
where they’re trapped and detected
by an array of specialized receptors.
Those can recognize odor molecules
at concentrations
of less than one in a million.
So what determines how strong
your body odor might be?
It depends on the resident microbial
populations in your armpit,
and the nutrients that
your glands provide them with.
Your genes help determine
what compounds you produce,
and in what quantity,
so everyone has a slightly different set.
In fact, a gene variant that virtually
eliminates body odor
is common in people of East Asian descent.
Adrenaline increases the ratio
of apocrine to eccrine sweat,
so body odor can be more intense
when you’re nervous.
Bacterial composition and concentration
also varies between individuals
and plays a part.
Even what you eat can have
a small effect on how you smell.
So how can we deal with body odor?
Washing the armpits with soap and water
helps but won’t remove all the bacteria
since many are buried
in deeper layers of the skin.
Deodorants, however, inhibit bacterial
activity and mask odors at the same time.
Antiperspirants work by forming tiny
gel plugs that block sweat glands,
drying out the armpits.
While we continue to battle body odor,
scientists are trying to understand it.
We don’t know why the brain
often interprets these particular
odors as off-putting.
But some researchers have proposed
that secretions from the armpit
could have a positive function, too,
like cementing social bonds
and providing a means
of chemical communication.
We don’t know yet if that’s the case.
For now, body odor seems to be
just another smelly part
of the human condition.
