Sweat seems simple enough. You’re stressed, aroused, working out, or simply wearing too many layers, so your body compensates by releasing a thin layer of stinky water to cool everything down. Pretty cut and dry, right? Well, not exactly. As it turns out, the science behind perspiration—like basically everything that happens in our weird and wonderful bodies—is way more interesting than you might have thought. From seemingly simple things why it smells, to more complicated questions like how it’s perceived by bystanders, sweat’s full of surprises. We’ve broken down a few of the more compelling factoids here. Because the more you know about your enemy, the easier he is to destroy—or just deodorize.

Sweat Doesn’t Actually Stink (On Its Own)

The logical assumption is that, since people start smelling nasty as they get sweaty, then it must be the sweat that gives off the odor. However, science tells us that that’s not really the case. Composed almost entirely of water, with only 1-2% being ingredients like salt, protein, fats and acids, perspiration is entirely odorless on its own. It’s only when sweat gets excreted—and subsequently processed by the bacteria that lives on your scalp, pits and groin—that its distinctive odor rears its ugly head. That is, what you’re smelling is actually the digestive byproducts of sweat-sucking microorganisms. Germ farts, if you will.

There Are Two Kinds of Sweat

First off, there’s what we’ll call your baseline sweat. You've dealt with it since you were a kid: it’s thin and clear, and doesn’t trigger much of a smell. Then there’s the nasty stuff. A bit thicker, oilier, and filled with stuff like proteins, fats and steroids, this junk only comes about once you’ve hit puberty. And the bacteria love it, thus the stank that we all have to deal with once we’re not kids anymore.

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This Is How Antiperspirants Work

Compared to deodorants, which simply seek to mask the foul stench emitted by your pits, antiperspirants act a bit more like medication, by altering the chemistry of your underarm to keep you from sweating. There are two specific things happening. First off, chemicals in antiperspirants mix with your sweat and hair to form a plug, keeping sweat from getting out. Secondly, antiperspirants often also contain some antibiotics, which kill off the microbes that make the stench. You know, just for good measure.

People Can Smell If You're Happy

Louis Armstrong used to croon, “When you smile, the world smiles with you.” Well, a recent study in Psychological Science says that might actually be true. In their experiments, a group of Dutch scientists tested people’s reactions when they smelled samples of perspiration from guys who watched films designed to make them happy. Their results: when exposed to happy sweat, increased activity was seen in the facial muscles that make you smile. Also, in general people responded with a more positive outlook when they smelled the happy sweat, as compared to to the control group. So keep on smiling, folks.

Actually, Sweat Can Convey a Whole Host of Emotions

When it comes to conveying how you feel, sweat isn’t limited to smiles and rainbows, though. No, sweat can actually signal a host of other emotions in those that get a whiff, from fear and disgust to anxiety, and even arousal. It does this using things scientists call chemosignals: chemicals that, when they evaporate, are inhaled by others and elicit a response. Smoke signals, kind of.

It Can Also Say What’s Going On Inside Your Body

Sweat doesn just tell us what’s going on inside your mind; it can let doctors know what’s happening in the rest of you. We can use sweat tests as a noninvasive means of monitoring drug use. At this point, though, other clinical applications are relatively limited, with the main issue being that it’s hard to collect enough sweat to test it. However, scientists are currently in the process of developing wearable monitors, which’ll help to test everything from athelete exhaustion levels to disease. So keep an eye out for those.

Sweat Plays a Role In Sex

Who finds you sexy might be more up to biology than you’d like. A 1995 study on subject of sweat and its role in attraction found that, when women were presented with the smelly t-shirts of a sample of men, they found the sweat of men whose immune systems most complemented theirs the most pleasant. This led scientists to believe that sweat might act as a kind of mating beacon, with women finding the men who could help them make the most genetically viable children more attractive than the rest. So, next time you get rejected, go ahead and chalk that one up to chemistry.

There Is A Clinical Definition of “Too Much Sweat”

It’s condition is called hyperhidrosis, and essentially it’s exactly what one would expect: those suffering tend to sweat to such a degree that it actually affects their day-to-day life pretty significantly. According to the National Institute of Health, people with the condition tend to have issues using things like keyboards and doorknobs, sweat through their clothes and can even have pretty severe skin issues from being so moist all the time. Luckily though, there are treatments, and they’re pretty effective. If this sounds all too familiar, go see a dermatologist who can help you out.

The Meat Sweats May Be a Thing

Then again, you totally knew that already.

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