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9 Totally Uncomfortable Facts About Sweat

What are you really smelling when you smell your armpits?

Posted on August 28, 2015, at 1:33 p.m. ET

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1. Your sweat feeds whole colonies of bacteria that call your body home.

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It turns out sweat is real tasty to a number of bacteria who specialize in munching on the lipids and fatty acids found in some kinds of human sweat. These bacteria consist of things like Staphylococcus, Corynebacterium and Propionibacterium species.

2. All that body odor you associate with sweat is really just the noxious waste produced by those bacterial feasts.

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Once those bacteria consume some of the chemicals in sweat, they convert them into volatile fatty acids (VFAs) and thioalcohols. Volatile means that these bad boys are airborne, so their nasty scent can travel far away from its source (you).

3. Very few animals outside of humans actually use sweat to keep their bodies cool.

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Many mammals sweat, but only humans, some primates, and ungulids (camels, donkeys, horses, and cattle) do it to cool themselves off. Other potential uses for sweat are the removal of toxins, for traction on the palms and paws, and the spreading of pheromones.

4. Sweating might not cool you the way you think it cools you.

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The mechanism that cools you when you sweat isn’t the sweat itself, but the evaporation of that sweat. This process is called evaporative cooling, and it occurs because the evaporation of water is an endothermic reaction, meaning it removes heat from the air around the skin to complete the evaporation thereby cooling the air directly in contact with the body.

5. There are different kinds of sweat.

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Humans produce three different kinds of sweat: Sweat to cool down (thermal sweating), sweat in response to emotional or sexual cues (emotional sweating), and sweat from eating food (gustatory sweating). Only the first kind happens in response to temperature.

6. ...And they come from different places.

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There are two main types of sweat glands in humans (plus one that is a hybrid of the two). Apocrine glands don’t develop until you hit puberty, and only occur in hairy regions like armpits as well as a person's genitals. Eccrine glands are the main glands in humans. They are all over and they do most of the thermal sweating for your body.

This difference is why genital and other hairy regions smell more!

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Sweat produced in these gnarly regions come from the apocrine glands, not the more common eccrine glands. Those glands produce more of the lipids and fatty acids that bacteria love so much. That's why your armpits and your unmentionables produce the lion's share of B.O.

7. The average human has around 200 sweat glands per square centimeter.

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That's a lot of glands.

8. The highest sweat gland density is found on the palms of your hand and the soles of your feet.

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There could be an evolutionary reason for this. Some scientists believe that sweat in these areas is triggered by fear and improves traction on the feet and hands of an animal allowing it to escape more swiftly. This could be why emotional sweating in humans generally affects your hands and feet more prominently.

9. An average human can sweat as much as 2.5 liters per hour.

Buckets. of. sweat.
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Buckets. of. sweat.

All things considered, though, you should be pretty pumped about sweat. It keeps us alive and helped us evolve into the stinky creatures we are today!


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