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  • A pungent blend of onions, cheese, and cat urine with hints thatwet 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.

A pungent blend of onions, cheese, and cat urine with hints thatwet goat?

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B2 US TED-Ed odor body odor body bacteria sweat

What causes body odor? - Mel Rosenberg

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    April Lu posted on 2018/04/08
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