October 13, 2020/Primary Care

Breaking a Sweat: Why You Sweat and What It Says About Your Health

The sweaty truth: why sweet smells turn foul

closeup of man's sweating face

We all sweat, and some of us do it more than others. Sweating is one of your body’s natural ways to not only cool itself, but also to rid itself of toxins. How much — or how little — you sweat can reveal clues about your health.


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Rachel Ward, MD​, helps us to understand which medical conditions, from menopause to stress and anxiety, can make you sweat, and when sweat can signal a serious medical condition that needs prompt attention.

Everyone has sweat glands, and they’re all over your body. You might not realize it, but sweat alone has no odor. Surprisingly, if you were to taste your sweat (eww!) you’d find it’s also sweet-tasting. One drop of sweat is about 99% water. The remaining 1% of sweat contains traces of urea, uric acid, ammonia, lactic acid, vitamin C and other substances.

Sweat is your body’s natural coolant. You make sweat in various situations. Maybe you work up a good sweat at the gym or during another vigorous activity. Or maybe you find yourself sweating before a presentation at work or school.

It turns out, there are two types of sweat that come out of two different types of glands during these different times.

  • Common sweat (eccrine): the light, watery sweat that happens when you’re active on a summer day. This type of sweat cools as it evaporates off your skin, and soaks your shirt when you exercise.
  • Stress sweat (apocrine): this type of sweat feels thick and actually contains fat. It’s produced during times of extreme stress and comes from the roots of body hair in your armpits, scalp and groin area.

Why does sweat create body odor?

Everyone has a personal odor. Normal amounts of bacteria on your skin interact with common sweat to create your personal scent. But when you have too much bacteria on your skin or in your clothes, this can cause what’s known as B.O.

Ah, yes, body odor. Maybe you’ve been in a locker room and smelled that distinctive scent. But what causes some people to smell funky?

“Sweat itself has no smell,” says Dr. Ward. “But when it comes into contact with bacteria on your skin, that’s when things begin to turn foul.” She says bacteria eat organic particles in your sweat and excrete digestive gas, and “what you smell is bacterial flatulence.”


Yes, you read that right! Bacteria farts! Ew!

If that’s not enough to make you run for the shower, consider this: When stress-induced apocrine sweat comes into contact with even normal amounts of bacteria, it can stink even worse. It’s your body’s extreme response to stressful situations. So, running to catch an almost-missed flight, or giving a big presentation for work? Better apply an extra bit of deodorant.

What about stinky feet?

We’ve all known someone with stinky feet. But did you know each foot has about 250,000 sweat glands producing an average of a pint of sweat a day! Lace that foot in airless leather or, even worse, man-made “pleather” shoes with all of your foot’s natural bacteria and fungus for eight to 12 hours and what do you think is going to happen?

“If your feet are prone to excessive sweating, it’s important to buy breathable shoes made of natural materials like leather or canvas,” Dr. Ward says. There are other things you can do to combat sweaty stinky feet, such as keeping your feet dry, buying breathable socks that wick moisture away from your skin. You can also use over-the-counter foot antiperspirant or corn starch in your shoes.

What if you can’t stop sweating? Or don’t sweat at all?

Some people seem to sweat excessively no matter what the situation. If you feel like you sweat more than normal amounts and nothing seems to help, you may have a condition called hyperhidrosis. You may experience hyperhidrosis over your whole body, or you might experience it in a more localized place, like your palms, feet, face or armpits.

There are several treatment options for hyperhidrosis.

On the opposite spectrum, you may notice you don’t seem to sweat, even after vigorous exercise. Anhidrosis is a medical condition where you are unable to sweat normally. Anhidrosis is often difficult to recognize and diagnose. You may inherit this condition genetically from someone in your family, or it can be caused by certain medical conditions such as diabetes, radiation therapy, heatstroke, certain skin conditions or even alcoholism.


Not sweating may sound awesome, but it can be serious and sometimes fatal. “If you’re unable to sweat, your body can’t cool itself, which can become quite serious,” Dr. Ward says. Treatment for anhidrosis involves pinpointing the underlying causes.

When sweating is more serious

A sudden outbreak of heavy sweating can also indicate serious medical issues, such as a heart attack. It’s also associated with certain metabolic issues, such as diabetes and some thyroid conditions. It can happen with some cancers. “The bottom line is, if you’re sweating excessively and nothing seems to help, it’s best to see your doctor,” says Dr. Ward.

What about deodorant and antiperspirants? What’s the difference?

Just like brushing your teeth, putting on deodorant is probably part of your every day getting-ready ritual. But shopping for personal care items can leave you feeling baffled by the body care aisle. You might see some deodorant sticks labeled as only deodorants while others are antiperspirants. What’s the difference and how do you choose the right one?

The difference is really quite basic. Deodorant does just that: keeps your odor at bay. Similarly, an antiperspirant does two jobs: it keeps odors at bay, and also keeps you from perspiring — thereby avoiding wet armpits (and other areas) during a stressful day. These products reduce your body odor caused by sweat and bacteria.

Recently, there’s been an increase in antiperspirants and deodorants labeled “aluminum free.” There was some speculation that the aluminum salts found in many antiperspirant/deodorants were linked to breast cancer. However, recent research has shown there is no definite link between aluminum and breast cancer. ​

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