Why do we sweat?

From meat sweats to cold sweats, here's everything you need to know about why we sweat and what we can learn from it

Do we talk enough about sweat? Some would argue not. But it plays an important role in our body and can tell us something about our own health. Dr Aoife Morrin from the School of Chemical Sciences in DCU joined RTÉ Radio 1's Brendan O'Connor to shed some light on why we sweat (This piece includes excerpts from the conversation which have been edited for length and clarity).

"A lot of the sweat that we produce, or at least the excretions from our glands, produce what we call volatile compounds or gases. The types of those compounds that we can detect, can start to tell us a little bit about what's going on inside the body," says Morrin.

But first, why do we sweat?

Sweating is mother nature's answer to thermoregulation: maintaining a constant temperature within our body, she explains. "I'm not talking about the temperature of our skin, I'm talking about the core temperature inside our body."

We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences

From RTÉ Radio 1's Brendan O'Connor Show, Dr Aoife Morrin from DCU on all things sweat

Sweating is a response by the brain to any increase in that core temperature. "Once the brain starts detecting an increase - we might be exercising, we might be in hot weather - what happens is it sends out a couple of responses for the body to regulate itself, one of those being a sweat response. That sweat response itself doesn't actually cool us down. But when the sweat reaches our skin and starts to be vaporised from the skin, that's where we start to lose heat as well. Because that process takes energy and that energy is a form of heat."

Why do we also sweat when we're nervous?

That's what we call a cold sweat. "When we get nervous, when we're in pain, when we're stressed, we move into what we call the flight or fight response. That sends messages out from the brain to do things to regulate our body, to bring it back to normal," says Morrin. This includes increasing our heart rate and our breathing pattern, as well as a release of sweat, mostly from the apocrine glands under our arms.

Are 'meat sweats' a recognised thing in the scientific community?

Yes, the meat sweats are real, but scientists don't call them that, Morrin says. "This happens when we eat maybe a very protein rich meal or a heavy meal, sometimes late at night, and it's particularly hard to digest. So our body has to actually work extra hard to digest that food and, in doing so, starts to release heat. Again, our core temperature increases, and these responses like heart rate increases and sweating, happen to try and regulate back to our homeostasis."

From TEDEd, science teacher John Murnan on the science of why we sweat

What's in our sweat and why does it sometimes smell?

There's a lot of things going on to give sweat its odour, says Morrin. "First of all, the sweat that we emit or secrete from most parts of our body is called eccrine sweat, and that's mostly water and some salts mixed in."

The sweat that we emit during cold sweats, but also for thermal regulation, comes from the apocrine glands, which are found in different places on the body, including under the arms, in the groin, and also in the ears. "The hairy bits, essentially," Morrin adds. "[The apocrine glands] release a different type of composition of sweat. That will have the water, it will have the salts, but it'll also have some proteins and some lipids in it."

Whether we're talking about eccrine or apocrine sweat, it's not the sweat itself that has an odour. "What happens is, there's bacteria all over our skin, and the bacteria use this as nutrients. They metabolise whatever is in the sweat and they themselves emit metabolites that have a smell."

From RTÉ Radio 1's Drivetime, consultant dermatologist at Tallaght University Hospital Ann Marie Tobin on the importance of sweating

Does the body sweat out toxins?

There's no evidence for that, says Morrin. "Some of my research is around the hypothesis that there are some toxins in particularly apocrine sweat or from sebaceous glands (which aren't involved in the sweat process). But typically, even if they're present they're present in very, very low concentrations. Really, we rely on other organs like our kidneys and liver for toxin clearance for our body."

So is there any point in going to the sauna to 'sweat out toxins'?

"There's lots of reasons to go for saunas. I, for one, absolutely love a good sauna. But the health benefit probably isn't around this toxin elimination that people might think it is. It's around increasing the body core temperature and increasing the dilation of our blood vessels."

"If we do that regularly enough, whether it be by saunas or maybe exercise, we lower our blood pressure because we increase the diameters of our blood vessels and that lowers our blood pressure in our body. So that is really the health benefit, and obviously has health benefits from the heart point of view, even from a neurodisease point of view. So although it's probably not clearing toxins from our body, it has a lot of health benefits. If you like it, do it."

From RTÉ 2fm's Jennifer Zamparelli show, when does sweat become a medical issue?

Why do some people sweat a lot?

The medical term for excessive sweating is Hyperhidrosis and there's lots of reasons why someone might experience it. "Excessive sweating essentially means your sweat glands are workaholics, if you like. They're working when you don't need them to. That can cause lots of distress for people and it's uncomfortable. But it's still within the normal spectrum most of the time."

"There are however a small set of circumstances where excessive sweating, and probably some other symptoms, are going to be reflective of something else going on in the body. Whether it be related to the heart or something." If someone feels they might have Hyperhidrosis the best advice is to talk to your GP. "The majority of time it is absolutely normal," she says.

Are there people who don't sweat?

It's very rare not to sweat, Morrin says. "Often, it might only come about because of surgery. Newborns don't have their sweat glands activated, so they can't thermal regulate very easily. Certainly not as well as us. Which is why we're always being told about newborns and not overheating them and so on. They start to develop their sweat glands quite early in life, as early as two weeks, actually. But they become much more efficient, and we train our sweat glands, and we activate more and more sweat glands as we age."

What can sweat tell us about our health?

"Cystic fibrosis, for example, is diagnosed through a sweat test because there's elevated levels of sodium in the sweat of somebody who has cystic fibrosis. Those tests then cannot be done until enough sweat can be produced by that body, which is typically around 2 weeks to a month," she explains. Sweat testing can also tell you about your hydration, as well as stress levels because cortisol can be present in sweat.

Follow RTÉ Brainstorm on WhatsApp and Instagram for more stories and updates

The views expressed here are those of the author and do not represent or reflect the views of RTÉ