Understanding Sweat and How to Control It
Sweat stinks, stains your clothes and can be embarrassing in public. But it’s vital to health, keeping our bodies cool during exercise, on a sunny day or when we eat certain foods such as chili.
We also produce sweat when we feel under pressure, as part of our stress response.
Here, the experts reveal the latest understanding of sweat’s role in health and how to keep your sweat under control.
OUR BODIES PRODUCE TWO TYPES OF SWEAT
There are nearly four million sweat glands in our skin which can produce up to 25 ml of sweat in an hour to regulate our body temperature — this can rise to two to four liters an hour during exercise, says George Havenith, a professor of environmental physiology and ergonomics at Loughborough University.
Experts in Britain say there are almost two million people in the UK that suffer from excessive sweating or hyperhidrosis. “They can’t function normally: they have to change their shirt every hour or can’t shake hands with people,” says Dr. Anton Alexandroff, a consultant dermatologist at the University Hospitals of Leicester NHS Trust.
We lose moisture through our skin all the time, but hardly notice it because the air makes most of the liquid evaporate quickly, according to Professor Havenith.
“People who say they don’t sweat are wrong,’ he adds. If we didn’t sweat, we would collapse and die half an hour into a run as our body temperature would rise too much.
‘The difference in sweat levels lies in how sweat is distributed between glands: some people feel it extensively as it all comes out of one area, for example, the forehead.
‘In individuals who say they don’t sweat, the perspiration is just more evenly distributed across glands, so doesn’t build up a layer of liquid that they notice,” he explains.
We produce two types of sweat — the watery sweat that cools us down, and an oily liquid that is linked to sexual attraction.
The cooling type of sweat is produced by the eccrine glands, found just under the skin all over the body. When your body heats up, the hypothalamus, the temperature center of the brain, instructing these glands to produce sweat: this evaporates on the skin, taking heat from our bodies.
“We produce seven times more watery sweat than the oily kind because of its role in protecting us from overheating,” says Dr. Justine Hextall, a consultant dermatologist at Western Sussex Hospitals.
This sweat is produced by filtering fluid in the eccrine glands. ‘”Salts are extracted back into the blood if they are needed, and the remaining salty liquid passes out as a fluid onto the skin,” explains Professor Havenith.
WHY TEENAGERS CAN BE SO STINKY
The apocrine glands produce the second type of sweat in the armpits, genitals, and nipples. They produce an oily liquid full of fat and protein — animal studies suggest this sweat contributes to sexual attraction.
Though it’s odorless when released, once this sweat is on the skin it quickly reacts with bacteria such as Staphylococcus hominis, producing the stench.
“A hairy armpit has a big surface for debris and bacteria to adhere to so tends to be more smelly,” says Professor Havenith.
East Asian’s typically don’t have body odor because they have a gene that keeps them from producing certain proteins that would be converted by bacteria into odors.
“This type of sweat can be triggered by hormones such as cortisol and is released at times of stress or extreme emotion. It’s part of our fight or flight response. ‘A small amount of sweat on our hands and feet improves the friction in our skin and helps us grip,” says Professor Havenith.
“Teenagers’ sweat tends to smell because their fluctuating sex hormones stimulate the apocrine glands to release oily sweat,’ says Dr. Hextall. ‘Because of the habits teens tend to have — such as not washing — odour-causing bacteria builds up.”
YOUR UPBRINGING AFFECTS SWEAT
Some sweat glands are more active than others. One theory is that heat exposure before the age of four determines how well your glands cool you down, says Professor Havenith.
“That’s why people who grow up in the tropics sweat more than those who holiday there, because more glands are active and these activated glands are also more efficient at cooling the body down, producing more sweat.”
Having a tattoo could also make you sweat less, as the inking damages sweat glands, according to a study published earlier this year in the journal Medicine and Science in Sports and Exercise.
TAKE HOT BATHS BEFORE VACATION
To reduce excessive sweating on vacation, prepare your body weeks before as athletes do, says Professor Havenith.
Before vacationing in a hot climate, many train their sweat glands to work more efficiently in high temperatures by working out in hot rooms. “Using a sauna or having a hot bath on a regular basis, can train your sweat glands to be more efficient at high heat, producing more sweat to cool you down, but distributing it better all over the body,” he says.
WHY OVERWEIGHT PEOPLE TEND TO SWEAT MORE
In general, overweight people tend to sweat more, says Dr. Alexandroff. They have to use more energy when exercising to move their body weight and they have a bigger surface area to cool down.
The more fat a person is carrying, the harder it is to cool down, and the more sweat they’ll need to produce according to Dr. Hextall.
Individuals who are fit also sweat more during exercise because their bodies have adapted and are more sensitive to temperature change thereby, becoming more efficient at sweating to keep the body cooler says Professor Havenith.
ANTIPERSPIRANT GOES ON AT NIGHT
If you shower daily you’ll remove harmful bacteria so you shouldn’t smell, says Dr. Alexandroff. Another trick is to use antiperspirant before bed. Women who do this have been shown to sweat less than those who use the products first thing in the morning.
Antiperspirants contain aluminium chloride. Aluminium particles are taken up by cells in the sweat glands, causing them to swell and close up, so they no longer release sweat. It is thought that by applying it at night, the antiperspirant has time to ‘set’ in the pores during sleep.
“Dry your armpits and apply antiperspirant at night,” says Dr. Hextall. “What’s left on the skin will irritate some people so in the morning, have a shower.”
“You can apply a deodorant for fragrance — even rub lemon juice into your armpits: studies suggest this can change the pH of skin so that some odor-causing bacteria that prefer alkaline environments don’t survive,” she adds. (Some experts have suggested aluminium may be linked to breast cancer, but this remains controversial.)
HAVE HOT DRINKS TO COOL DOWN
Some people can sweat more when eating foods such as peanut butter — this is thought to be a mild allergic reaction. “The body may perceive certain triggers as harmful and flush them out through sweat,” says Professor Havenith.
Hot coffee or tea can also make you sweat as it stimulates temperature sensors in the body, which set off your body’s cooling mechanism. And caffeine can stimulate the nervous system to activate sweat glands.
In fact, hot drinks may be better at cooling you down than cold ones, says Professor Havenith: “We produce more sweat in response to a hot drink than with a cold drink, which suppresses sweating and doesn’t change our body temperature.”
Chili can make us sweat because it contains capsaicin, a chemical that stimulates nerves in your skin and mouth that detect heat. “Body temperature hasn’t changed, but the nervous system has been fooled by these chemicals,” explains Professor Havenith.
YOU SWEAT WHAT YOU EAT
What you eat can affect sweat odor. Garlic or asparagus can give off a smelly odor because chemicals in these foods are not adequately broken down and are released in breath and sweat, says Dr. Alexandroff.
BEING SMELLY MAY PROTECT YOU
Diabetes and other metabolic conditions can alter your body odor. This is because they lead to a build-up of toxins in the blood which are transmitted in your sweat, which can then be detected as acidic or rotten apple scents, explains Professor Havenith.
Patients can also get nerve damage as a result of uncontrolled blood sugar levels. This, in turn, can affect the nerves surrounding sweat glands, and cause them to sweat excessively, says Dr. Hextall.
The upside to the odor is that you’re less likely to become dinner for mosquitos, according to a 2005 study by Rothamsted Research and the University of Aberdeen. Researchers found people who don’t get bitten produce chemicals that can ‘mask’ the scent of lactic acid, a waste product from your body that attracts mosquitoes.
High-protein diets can also lead to malodorous sweat, particularly if you’re exercising, adds Dr. Hextall. “If you don’t have enough carbs your body will start to break down protein as fuel, which releases ammonia in sweat, leading to an ammonia-like smell.
‘This scent could also indicate that the liver or kidneys aren’t working properly.”
MEN AND WOMEN SWEAT THE SAME AMOUNT
The prevailing theory is that men sweat more. But a study conducted by the University of Wollongong in Australia suggests sweating is linked to your body size. Smaller people, regardless of their gender, increase blood circulation to their skin to lose heat, sweating less.
TRY SWEAT TRANSPLANTS
For some, the issue is not down to excess sweat but the wrong type of bacteria on their skin causing excess odor. Earlier this year researchers at the University of California suggested treatment for this: a ‘bacterial transplant.’
Scientists studied identical twins, one with body odor, the other without. They took a swab of bacteria from the fresh-smelling twin and smeared it into the armpit of the smelly one. The scent disappeared, even a year later. The theory is that the new bacteria outnumbered the bad, eliminating the odor.
‘It is like a probiotic that improves odor,’ says Dr. Alexandroff.