Sweat

What is sweat?

Sweat (perspiration) is a salty substance that glands in your skin make to keep your body temperature at a healthy level. Sweating is a normal part of life. It prevents your body from overheating and allows you to safely exercise, work outdoors in the heat or live in a warm climate. Certain health conditions and medications can affect your body’s ability to sweat normally. For example, you might sweat more than expected. Or your body may be unable to produce enough sweat to cool itself.

And — this might be hard to believe — sweat itself doesn’t stink. It actually doesn’t even have a smell. The odor is produced when bacteria that naturally live on your skin start breaking down the sweat.

Learning why we sweat and the anatomy of your sweat glands can help you understand what’s going on inside your body when your shirt gets damp in the summer, or when you can’t stop wiping your hands on your shirt before giving a presentation. Sweat isn’t always convenient, but it’s a substance that helps your body function.

Reach out to a healthcare provider if you have concerns about how much — or how little — you’re sweating, or if you notice changes in when or how often you sweat. They’ll help identify what’s going on and recommend treatment or lifestyle changes tailored to your needs.

What does sweat do?

Sweat’s main function is to regulate your body temperature (thermoregulation). Sweat naturally cools your body down when needed — like when working out or spending time in the sun — so you don’t overheat. When sweat reaches your skin, it evaporates (turns from liquid to gas), and this process cools your skin and the tissues underneath.

The process of sweating helps keep your body temperature at just the right level — not too hot and not too cold. This is typically around 98.6 degrees Fahrenheit (37 degrees Celsius).

Sweat also has other functions like:

• Hydrating your skin. Sweat contains substances, like amino acids, that act as humectants. This means they lock in moisture at your skin’s surface to keep your skin from drying out.
• Protecting your skin against infection. Sweat contains antimicrobial peptides. These are natural chemicals that help your immune system ward off invaders like bacteria or fungi that might try to enter your skin.

What are sweat glands?

Sweat glands are small structures within the layers of your skin that make and release sweat. They’re a type of exocrine gland, which is a gland that releases substances through openings (ducts) onto the outer surface of your body. Each sweat gland has two main parts — a secretory coil that produces the sweat, and a tube-like duct that sends the sweat toward your skin’s surface.

There are two specific types of sweat glands:

• Eccrine sweat glands: Most of your sweat glands are eccrine, and they’re spread out all over your body. They’re the main glands responsible for regulating your temperature. They produce the light, watery “common sweat” that evaporates from your skin to cool you down. They also jump into action when you’re feeling a strong emotion. Eccrine glands release sweat directly onto your skin’s surface.
• Apocrine sweat glands: These produce “stress sweat” that’s thicker and sticker, typically in moments when you’re anxious or nervous. They play a minor role in cooling you down. Apocrine glands are mostly located in your armpits and genital (perineal) area. They release sweat into your hair follicles, and from there, the sweat travels up the follicle until it reaches your skin’s surface.

What’s sweat made of?

Your eccrine glands produce sweat that’s about 99% water. That’s why the sweat you notice on a hot day feels so watery and evaporates quickly. We think of sweat as salty because sodium and chloride (the two components of table salt) make up most of the remaining 1%. Sodium and chloride are key electrolytes that do important jobs in your body. But the following substances are also present in smaller amounts:

• Potassium.
• Vitamins.
• Trace minerals like calcium, magnesium, copper, zinc and iron.
• Proteins and amino acids.
• Toxins like heavy metals and bisphenol A “BPA” (very small amounts).

Your apocrine glands produce sweat that’s thicker and stickier than eccrine sweat. It’s still mostly water, but unlike eccrine sweat, it’s rich in fats (lipids). It also contains proteins, sugars and ammonia.

Is sweat always salty?

Yes, your sweat always contains salt (sodium and chloride), but the concentration can vary. Your sweat is saltier when your glands produce more sweat within a shorter period. In other words, it’s saltier when your sweat rate is higher. A higher sweat rate is necessary when you’re more at risk of overheating, like when you exercise vigorously or in intense heat.

To understand how much salt is in your sweat, it helps to know about another function of your sweat glands: salt reabsorption. Essentially, these glands take back some salt to prevent too much from leaving your body. It’s like a chef who tinkers with the ingredients before serving the final product.

Your glands start out by making “primary sweat.” This contains all the same stuff as the sweat you see on your skin but has higher levels of sodium and chloride. This primary sweat travels up through your sweat gland’s duct (the tube-like portion). The duct is lined with cells designed to absorb sodium and chloride in the sweat that passes through. And voila — primary sweat transforms into a less salty sweat before it reaches your skin’s surface.

But let’s say you’re jogging on a hot day and sweat is pouring from your body. In this case, your sweat rate is higher than usual — and your sweat glands must work hard to keep up. There’s less time to tinker with the ingredients. Similar to line cooks on a Saturday night, your sweat glands just have to keep things moving. They can’t take out as much sodium and chloride as usual. So, the sweat that makes its way to the surface is saltier than it otherwise would be.

Salty sweat as a biomarker

A biomarker is a sign that healthcare providers use to diagnose a medical condition. The concentration of salt in your sweat is a biomarker that helps providers diagnose cystic fibrosis (CF).

People with CF have saltier sweat. This is because they’re born with mutations to the CFTR gene that, among other things, prevents their sweat glands from reabsorbing as much salt as expected. A sweat test — which measures the amount of chloride in a person’s sweat — is the conclusive way to diagnose CF.

What’s involved in the process of sweating?

Your body’s sympathetic nervous system manages the process of sweating. There are two types of sweating — thermal (in response to raised body temperature) and emotional (in response to your emotions).

Thermal sweating

Thermal sweating begins when the “sweat center” of your brain (a specific part of your hypothalamus) detects that your body is warmer than it should be. This could be internal body temperature or external body temperature. Internal body temperature is a stronger trigger, but a spike in skin surface temperature can also activate it. Your internal temperature can go up at various times, like when you’re working out, sleeping in a hot apartment or gardening in the sun. 

Once your brain is activated, it sends out chemical messengers called neurotransmitters that tell your sweat glands to produce sweat. One specific type of neurotransmitter called acetylcholine binds to cells on your eccrine glands to stimulate sweat production. This is called cholinergic stimulation.

Usually, eccrine glands all over your body are involved. This means you sweat all over, not just in one or two spots. When your body cools down, your brain stops sending out the SOS for your glands to produce sweat and sweat production returns to normal.

Emotional sweating

Your sympathetic nervous system also controls emotional sweating, but in this case, the trigger is an emotion rather than a rise in body temperature. Although it’s possible to sweat all over your body, emotional sweating usually occurs in just one or two areas. The most common areas are your armpits, the soles of your feet, the palms of your hands and your forehead.

Acetylcholine is responsible for triggering most of your body’s sweat production. But other neurotransmitters, including epinephrine and norepinephrine, are also involved. They stimulate your apocrine glands in a process known as adrenergic stimulation (“adren” represents adrenaline, which is another word for epinephrine). Apocrine sweat mostly gets produced in response to emotions, and it plays just a minor role in cooling you down when you’re too warm.

What conditions and disorders are related to sweating?

Sweating disorders that might affect you or a loved one include:

• Primary hyperhidrosis: Hyperhidrosis is the medical term for excessive sweating. Primary hyperhidrosis is a chronic skin condition that involves excessive sweating in specific areas like your face, armpits, feet and hands. A genetic variation causes this condition, which typically starts before age 25.
• Diaphoresis: Diaphoresis is the medical term for excessive sweating due to an underlying condition or medication. It’s also called secondary hyperhidrosis. This condition typically affects your entire body, not just specific areas. You’ll likely have other symptoms, besides sweating, and those symptoms vary according to the underlying cause.
• Anhidrosis: This is when one or more areas of your body can’t produce sweat normally. It’s possible that other areas of your body can pick up the slack and produce enough sweat to cool down your body when needed. But with severe anhidrosis, your body can’t sweat enough to regulate your body temperature. This puts you at risk of serious heat-related illnesses like heat exhaustion and heat stroke.
• Bromhidrosis (body odor): Body odor happens when bacteria that live on your skin break down sweat as it reaches your skin’s surface. Body odor is common and often temporary — maybe you had a grueling workout or spent two hours in a tense meeting. But if you notice a change in your body odor or a persistent unpleasant scent despite showering and changing your clothes regularly, it could be a sign of an underlying condition like diabetes, liver disease or kidney disease.
• Heat rash (prickly heat): This is an itchy rash that forms when sweat gets trapped in the pores and ducts beneath your skin. It’s common among babies (whose sweat glands are still developing), adults who live in humid climates and people on bed rest.
• Hot flashes and night sweats: These are common symptoms of perimenopause and menopause. A hot flash is a sudden, uncomfortable flare of heat and sweating. It might be so mild you barely notice or so severe that it stops you in your tracks. Night sweats are when you wake up drenched in sweat. Hot flashes and night sweats can be symptoms of many other medical conditions besides menopause. They can also occur as a side effect of medications. Talk to a healthcare provider if you’re having these symptoms and aren’t sure why.

Is sweating a symptom of a heart attack?

It can be. Sudden, excessive sweating is a common symptom of a heart attack. You’ll typically have other symptoms, too, like chest pain (or pressure or tightness), nausea, vomiting and shortness of breath. But it’s possible for sweating and nausea to be the only symptoms of a heart attack, especially in people assigned female at birth (AFAB).

Sweating can also be an early warning sign in the hours or days leading up to more dramatic or “classic” heart attack symptoms. In this case, you might feel cold sweats along with other subtle symptoms like chest pressure, unusual fatigue or pain in your arm, jaw, neck or back.

If you think you might be having a heart attack, call 911 or your local emergency number immediately. The sooner you get medical care, the better your chances of surviving and minimizing damage to your heart muscle.

Is sweating good for you?

Sweating is good for you in the sense that it keeps your body temperature at a healthy level. But forcing yourself to sweat a lot to “sweat out toxins” or improve your overall health may do more harm than good.

This is because, when your body quickly loses lots of water (in this case, in the form of sweat), you can run the risk of dehydration and related problems like an electrolyte imbalance. If working up a good sweat makes you feel great, be sure to replenish your body with electrolytes.

But don’t expect that sweat session to rid your body of high levels of toxins. Your sweat is made of 99% water. The remaining 1% includes helpful (not toxic) substances like electrolytes and very low levels of toxins like heavy metals and BPA.

That means the amount of toxins that leaves your body is quite low — even if you’re dripping in sweat. There’s currently not enough scientific evidence to prove that sweating excessively — through exercising or using a sauna — purifies your body or improves your health. Studies that show such benefits may have flaws in their methods or other aspects that make their results less convincing to most scientists.

Your liver and kidneys are responsible for most of the “cleansing” you need to stay healthy. These organs remove toxins and waste from your blood that later come out in your pee. Despite the lore, sweat plays a pretty minor role in cleansing your body of harmful substances.

If you want to try workouts — like hot yoga — that make you sweat more, or you want to start using a sauna, check with a healthcare provider first. They’ll make sure your plans are safe for you according to your medical history. They’ll also discuss any possible benefits and risks with you.

Why don’t I sweat?

You might not think you’re sweating, but even when it’s not obvious, your body is releasing small amounts of sweat to regulate your body temperature.

If you feel like you’re not sweating at times when you should — like when exercising or outdoors in the heat — it’s possible you have a medical condition called anhidrosis. This means your body can’t produce sweat as expected. You should talk to a healthcare provider about what you’re noticing so they can determine the cause.

Lack of sweat that seems to come out of nowhere could mean you’re severely dehydrated or experiencing non-exertional heatstroke. Non-exertional heatstroke can happen due to age (people age 65 and older have an increased risk) or underlying health conditions. It often develops over several days.

Call 911 or go to the emergency room if you’re not sweating and have one or more of the following:

• A fever of 103 degrees F (39.4 degrees C) or higher.
• Skin that’s red, hot and dry.
• Muscle twitching.
• Nausea.
• Fast pulse.
• Dizziness or fainting.
• Seizures.
• Confusion.

A note from Cleveland Clinic

Don’t sweat the small stuff? Easier said than done when your shirt is soaked and you’re about to meet your boss for a performance review. But while sweating in stressful moments may seem more annoying than helpful, sweating that occurs at other times — like when you’re working outdoors in the heat — is necessary for survival. It’s easy to forget how important sweat is for our health, especially when we’re all so focused on getting rid of it.

Even though sweating keeps your body at the right temperature, sometimes things can go awry, and you might sweat more or less than needed. If this happens to you, a healthcare provider can help you find the best treatment. Don’t hesitate to reach out to a provider at any time if you have questions or concerns about sweat or how it’s affecting your life.