Everything You Wanted to Know About Sweating, Sweat Rates, Reduction – and More!
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Sweating, especially in the context of fitness, is one of those topics which divides opinion.
For some people, a covering of sweat is a badge of honour. It is a testament to their work ethic – evidence that they pushed hard this time. For others, it is an embarrassing stain on their workout gear – something to be avoided at all costs.
Most of us are in-between these extremes. Though excessive sweating is seen as something to be controlled, rather than enjoyed.
At work, in social settings and even walking down the street – visible perspiration or sweat patches take on a new level of horror!
This page digs deep into the topic of sweat.
This is a long guide. It is divided into five sections. Where you see links within the text to external sources, these will open up a new tab. This will allow you to continue reading – while saving the citations / science papers for later. Here are the five parts:
- Physiology of Sweat: The two separate types of sweat are introduced here. You’ll find out what makes them unique. How the sweat system is triggered, the purposes of sweating and how bad smells occur are all covered.
- Sweat Levels: This section explains ‘normal’ sweat levels and individual variations within them. Rehydration, electrolyte recovery and extreme sports are also covered.
- Hyperhidrosis: Excess sweating can become a medical issue. Primary and secondary hyperhidrosis are explained here. You will also find info on drugs / medications for medical sweating.
- Reducing Sweat: Strategies for managing sweat are divided into 3 sections. These are clothing, food / drink, simple physical interventions and medical interventions.
- Sweat Facts: I have ended the guide on a light-hearted note. You’ll find 10 fun facts and anecdotes about sweat here.
Section 1 – The Physiology of Sweat
We sweat to cool down. This is our primary cooling method. Water on the surface of the skin evaporates, taking heat with it.
A mix of our core body temperature and average skin temperature determines how much we sweat. The system (for most people!) is finely tuned. As temperature increases, more sweat glands are bought online. I have explained how those glands work, and their trigger mechanisms, below.
Sweating has a secondary purpose.
It is a way of removing substances from our body. These include salts and urea. While sweat being the same as urine is a major misconception, they do share a base in the form of urea. This is an organic compound, which is formed in the liver. Its role is to remove ammonia from the body.
Two Types of Sweat Gland
Most people think of sweat as one thing. In fact there are two distinct types, produced by different types of sweat gland.
Your body has between 2 and 4 million sweat glands. They fall into these categories:
Eccrine Glands: These are the most common type and cover most of your body. They are densest on the soles of your feel and your palms. Eccrine glands produce a watery sweat. This is made from water, with trace amounts of salt.
Apocrine Glands: These are found in your armpits, the genital region and in smaller numbers on the nipples and eyelids, sides of the nose and ear canals. Apocrine glands produce sweat which contains fats, proteins and ammonia as well as salts. This is a thicker, stickier substance. Microbes love apocrine sweat. It the breakdown of this by microbes which produces bad smells. Apocrine glands are not active in children. These start to become active at puberty.
There are trace numbers of sweat glands which show properties of both types. These are labelled ‘Apoeccrine’.
How Sweat Glands Work
Both types of sweat gland contain a coiled section. This holds the liquids, salts, nitrogen bi-products and other trace substances. There is also a layer of myoepithelial cells around the coil, these contract when triggered via the central nervous system.
The secretion method (how the sweat leaves the cells of the sweat glands) depends on the gland type. For Eccrine glands, this is called ‘exocytosis’. It involves transporting water-soluble substances to the cell membrane, and expelling them. With Apocrine cells, part of the cell is broken off to transport sweat to the surface of the skin.
Triggering Sweat: Both types of gland are triggered by acetylcholine. This is released when the hypothalamus (an area in your brain) detects that we are overheating. The hotter we get, the bigger the response in terms of acetylcholine – with more sweat glands getting triggered. This causes the sweat ducts to dilate, and the secretion of sweat to begin.
Apocrine sweat glands are also triggered by adrenaline (epinephrine). This is released at times of stress.
As you can see in the picture, apocrine cells use the ducts associated with hair follicles as their path to the surface of the skin. Eccrine cells have their own ducts. The ends of these are more commonly known as your pores.
Why Do We Get Smelly Armpits?
Sweat does not smell. It is the breakdown of that sweat by microbes which causes that distinctive pong. The armpits are the primary spot for these smells for several reasons:
- Predominance of apocrine sweat glands
- Can get hot down there, with no air access much of the time
- Hairs (which trap the moisture)
When you sweat, the bacteria start to have lunch. They release methane containing fatty acids, steroids and sulphurous chemicals as by-products. These cause those distinctive bad smells. These microbes can swell in numbers very quickly when there is a ready food source.
Here are the main types of bacteria you will find feasting in your armpits:
Corynebacterium: Members of a large species of ‘club shaped’ bacteria love apocrine sweat! Their feasting produces methane compounds and fatty acids.
Staphylococcus Hominins: Makes things worse by adding ‘thioalcohol’ compounds to your underarm odours.
Getting rid of every microbe on your skin is impossible. There are billions and billions of them. Fortunately, there are strategies for reducing their numbers in key areas. This is covered in section 4 below.
Section 2 – Triggers for Sweating / How Much Sweat is Normal?
Average body temperature (core and skin) the main trigger for sweating, though it is not the only one. Here are the other triggers:
Fight or Flight Response: Stress and anxiety cause an instant sweat reaction. This reaction varies a lot between individuals. The origins come from a threat response mechanism which would have helped our distant ancestors survive. The threat produces Adrenaline (Epinephrine) which causes increase heart rate and opens the ducts of your sweat glands, instantly discharging the contents. How sensitive you are to insults, setbacks and challenging situations (public speaking for example) has a big influence on your sweat response. Visible sweat makes the stress situation worse for many people.
Chili / Hot Spicy Food: I have personal experience with this one. A curry or hot pepper sauce makes my forehead and scalp drip within seconds. This response comes via the spice Capsicum, which binds to the heat receptors on your tongue. The localised (head and scalp) sweat response is triggered. While I wish this did not happen, my love of spicy food means I’ll just have to deal with it!
Menopause: Night sweats and even sudden hot flashes associated with daytime sweating are experienced during the perimenopause and menopause. This is a complex topic, you can find out more about the physiological implications here.
Drugs / Medication: Treatments for depression (Serotonin reuptake inhibitors and others), anti-anxiety drugs, insulin and other drugs have been associated with increased sweat rates. As well as medical interventions, recreational drugs including amphetamines and cocaine may also increase sweating.
Obesity: For people carrying excess weight, the body needs to work harder in general. Getting from A to B involves more effort. This extra effort increases body temperature more, increasing sweating. As those of you that are fit will know, the opposite is also true. The fittest people also sweat more easily! More on that below.
Normal Sweat Amounts
During an average day, every one of us sweats around half a litre (1 pint). This is spread out over 24 hours, and all over the body – making it barely noticeable for most of us. There are individual differences. Some lighter sweaters might only make 0.3 litres (or even less) while a heavier sweater could lose up to 0.7 litres. This is before considering exercise, anti-perspirants, clothing, outside temperature and many other factors.
Sweat Amounts While Exercising
Sweating really starts to kick in when we exercise. Here there are even bigger variations.
0.8 litres per hour is a low baseline, though some individuals will sweat up to 2 litres per hour during an ‘average’ workout session. You can find out your own sweat rate (see below), and use that as a baseline for fluid replacement.
You need to factor in the intensity of your workout, and your (individual) propensity to sweat.
If you are fit, you’ll sweat sooner and at higher volumes than someone less fit. This is a positive thing, your body learns the cues for the need to cool – and that additional sweat allows you to keep cooler for longer, and so work out better. This is compared to an ‘average’ person. Someone completely unfit, obese (or both) will have to work very hard when starting sports / fitness. This will lead to more sweat too.
How well hydrated you are before working out will also affect your sweat levels. If you are low on water, your different body functions will start to compete for it. This leaves less water available for sweating. Performance will be negatively impacted if you are not well enough hydrated.
Environmental factors, alternative ways of cooling (ice, cold water, fans, clothing and so on) also need to be factored in.
The take-away is that you should be replacing up to 2 litres of liquids (and electrolytes) for each hour of working out.
Finding Your Own Sweat Rate
With a little effort, you can find out your personal sweat rate. Many factors (how hard you work out, weather and so on) all play a part. This means you’ll only have a broad idea of the number. This can be useful in comparing your rate to the averages. More people think that they are above average sweaters, which mathematically can’t be true.
Here is how to check:
Prepare / Weigh-in: Make sure you are hydrated, and have urinated before you weigh in. You then weigh yourself wearing minimal clothing, the more accurate your scales the better.
Work Out: Put your workout gear on, then do 1 hour of your usual exercise routine. If you consume any fluid while working out, this needs to be measured and recorded. Don’t stop to urinate.
Weigh Again: You’ll need to go back to the minimal clothing worn during your original weigh-in. Recheck that weight. Your sweat loss is 1 litre per kilogram of weight lost. You can convert this into pounds and pints afterwards. If you prefer those older units of measure, then this calculator will do the maths for you. If you did drink while exercising, don’t forget to subtract this extra liquid from your final weight.
I recommend repeating this on different days and with different activities. This will give you an idea of how your sweat response adapts to climate, workout type and effort levels.
Extremes – The Sweatiest Individuals, The Sweatiest Sports and Saunas
Let’s take a break from the science for a moment. If you have ever wondered just how extreme sweating can get, here are some entertaining numbers:
Marathon Runners: How Much Fluid is Lost During a Marathon? Research has shown that pro runners can lose an average of 2.3 litres of fluid per hour. Even for the ‘average’ runner, 1.5 litres, taken over 4 hours this would be 6 litres lost!
Tour de France: Top cyclists can lose up to 7 litres of fluid every day. I am not sure how scientists would factor in the effect on sweat of the different performance enhancing drugs allegedly used in cycling events…
Sauna: This may not be exercise in the traditional sense, though many similar health benefits are claimed. You can lose up to half a litre of sweat in as little as 20 minutes in a sauna. With skin temperatures at 40 degrees and humidity high, it is no surprise.
Triathlon: A lot of variables to consider here. How long each section is, the fitness levels of competitors and weather conditions. Even a ‘short’ triathlon can last up to 5 hours, with sweat rates for the different parts averaged at 1.5 litres per hour – this could be a huge 7.5 litres of fluid and the associated electrolytes lost.
Rehydration After Exercise – Electrolytes and Fluids
Replacing the fluid lost during a workout misses some vital ingredients. When you sweat, you lose substances collectively known as ‘Electrolytes’. These include Sodium (salt), Potassium, Calcium and Magnesium (plus some others).
Together, these electrolytes control how much water you retain, and the flow into and out of your cells. They are vital to core internal functions including sweating, muscle contractions and digestive + urinary functions.
If you replace only water, your electrolytes can get low. This causes an overall decrease in performance. It can also lead to complications like those nasty muscle cramps. In extreme cases, your sodium levels get so low compared to the water in your body, that you poison yourself with water.
Hyponatremia: Water poisoning can be fatal. In a condition called hyponatremia your salt levels are too low to prevent your cells absorbing too much water. The effect is swelling. If your major organs (especially the brain) starts to swell, a major medical intervention will be required.
There are sports drinks which will help replace those electrolytes fast. Keep in mind that many brands contain a lot of processed sugar (increasingly regarded as a poison). A clean and balanced diet will help keep your electrolytes in check. If you are a professional who wants to replace these on the go – then there are supplements available.
Other Factors Which Affect How Much You Sweat
If you made it this far, I’m sure the message that those of us who sweat more are (on average) fitter and healthier will be clear!
I’ll close out with your genes.
Even though there are complex dietary, environmental, psychological and medical reasons who some people sweat more than others – the primary driver is your genes. Some of use simply sweat more than others.
This is cold comfort for readers who are embarrassed or worried about their sweat levels. Part #4 below covers how to make the best of the hand you were dealt.
Before that, a quick look at the line between excessive ‘normal’ sweating and this becoming a medical issue.
Section 3 – When Sweating Becomes a Medical Issue
Our bodies are complex machines – and the systems controlling sweating can go wrong.
Hyperhidrosis is the collective label for sweating which has gone beyond the usual limits, and become a medical problem for the individual. There are other sweat-related conditions too.
What is ‘medically excessive’ sweating and just ’nuisance’ sweating is often down to the individual. If excessive sweating is making your life unpleasant, then this is a medical problem. If you can manage it, then, well, maybe it is not!
Hyperhidrosis can affect any part of the body, though it is most common on the palms and the soles of the feet. These are the areas where eccrine sweat glands are most densely packed.
Hyperhidrosis can be localised or general (affecting more than 100 square centimeters). It can also be linked to a stress / anxiety response. This can be divided into primary and secondary. Secondary hyperhidrosis is caused by other medical issues. Examples include some cancers, diabetes, thyroid issues and Parkinson’s disease.
Medical Treatments for Excessive Sweating
The main way to treat hyperhidrosis is to reduce the central nervous system messages which trigger the sweat glands. This is done by stopping the neurotransmitter acetylcholine from binding to receptor nerve cells. These drugs are collectively known as Anticholinergics. Within this category, there are drugs to treat gastrointestinal problems, depression and respiratory problems. Anticholinergics used for treatment of excessive sweat include propantheline and oxybutynin.
There are limitations – particularly for hyperhidrosis caused by severe anxiety responses. There are also side effects, include water retention and a dry mouth to consider.
These drugs are prescription-only, so you’ll have the opportunity to discuss their suitability with your doctor before taking them.
Stress / Anxiety Sweating Treatment: Beta blockers have the effect of reducing anxiety. While this is not a primary treatment for hyperhidrosis, it has been shown to help in stress-related excessive sweating scenarios.
There are other medical interventions. These include adding Botox (botulinum toxin) to the affected areas. Surgery is used as a last resort. This physically separates the sweat glands from the nerves, effectively preventing the sweat response from being triggered.
Section 4 – How to Effectively Reduce Sweating?
This is a big section. There are many weapons available to help you reduce sweat. Collectively, these strategies involve ‘managing’ sweat.
You’ll find 4 sections below. They cover clothing, antiperspirants, simple physical interventions and medical interventions. Mix and match these strategies as your personal situation requires.
Best Clothing / Fabrics for Hiding Sweat?
There are some advanced new fabrics around these days. These are focused on workout gear, and will diffuse sweat. The basics of smart use of clothing to reduce sweat are not so high-tech!
Colour Choices: Dark colours and white are best for making sweat patches less visible. Dark clothes do have a drawback. They reflect less sunlight, which means you’ll feel hotter. If you suffer from visible sweat, bold and bright colours need to be avoided. These will show under-arm (or other) patches right away.
Undergarments: If you wear a shirt or blouse for work, it is hard to hide sweat. Simple cotton undershirts are the best solution. Sure, an extra layer is not ideal, since the added heat leads to increased sweat. Choose cotton to absorb the moisture, and even change this half way through the day if required.
Sleeveless Tops: An idea for those who sweat heavily while working out. You can avoid underarm patches entirely, simply by removing the underarm material. You might feel odd in a muscle top / camisole / vest / singlet (or whatever you call it in your location) first time around, though this solves things easily for a lot of people.
Natural vs Man Made Fabrics: Cotton feels cooler, though if you do sweat into it, that sweat will find it hard to escape. Many polyester fabrics diffuse sweat better, these repel the moisture – rather than absorb it. These become smelly faster, as the microbes stay in them and you can’t wash them too hot!
Advances in the weave and the chemical composition of fabrics has moved on significantly. You can now get sportswear which is breathable, and will diffuse sweat while you are working out. This includes the Nike Dri-Fit range and many others. Those same advances have been used on natural fibres. These are used along with man-made ones to form composites. You will also find technology added to traditional fibres – for example Merino wool – creating some cool, breathable, sweat-diffusing alternatives.
AntiPerspirant: The Chemical Solution
The idea of antiperspirant is simple. You block the ducts which produce sweat, reducing the overall level. Many brands also contain alcohol, salts and other substances which reduce the number of microbes. Add a pleasant smell, a brand name and some marketing, and you’ll soon see how the antiperspirant business has turned into a $20 Billion / year industry!
There are several active ingredients used these days. The main types are aluminium chloride and aluminium chlorohydrate. These chemicals are found in most over the counter spray-on or roll-on (stick) type products. They block the ducts of the sweat glands, physically preventing the sweat from getting out by forming a temporary plug. Other aluminium-based compounds can also be found in over the counter anti-perspirants. These include the long-winded ‘aluminium zirconium tetrachlorohydrex guy’, and others.
The compounds found in antiperspirant need to find their way to the pores and join with sweat to form a plug. This means applying them while you are sweating heavily will be less effective. You might also find underarm hair stops the chemicals from reaching their targets. One study showed that just before you go to bed is the best time to apply antiperspirant. Personally, I think this is headline grabbing nonsense. Once you take into account the 8 hour+ time gap, plus a shower in the morning… you’d almost certainly want to apply again before work!
Many brands combine plugging sweat glands with killing smell-producing microbes. Alcohol has this effect, as do salts – for example sodium chloride. The finishing touch, a pleasant fragrance!
Are AntiPerspirants Safe?
The safety of chemicals found in antiperspirants is a concern for many people. There are persistent rumours that deodorant or antiperspirants are linked to increased incidence of breast cancer. This has been linked to ‘Parabens’ (a preservative chemical). No scientific evidence exists to support this, and even the original ‘scientific’ study failed to use basic checks and balances by not using any control group. In fact, the American Cancer Society has gone as far as to publicly refute rumours of a link. Please do your own research if you have any concerns.
Aluminium compounds may not be helpful for people with existing kidney disease.
Regular AntiPerspirant Not Effective? Go the Prescription Route
If using a regular antiperspirant still leaves you with damp patches, then you can go the prescription route and get a product which contains as much as 20% aluminium chlorohydrate. Speak with your doctor about this option.
Are There Natural Alternatives to AntiPerspirants?
Natural alternatives are available. They usually focus on the deodorant and microbe reduction area – managing bad smells. These range from corn-starch based ointments, to charcoal and even witch hazel. Even the people who advocate these suggest ‘rotating’ them. This keeps the microbe colonies from adapting and those smells from returning.
Alcohol based washes, vinegar and salt water can be effective for keeping microbe / bacteria populations down. These will not stop you sweating, though they may keep the smells away for a while.
Simple Physical Interventions
Armpit Shaving: Shaving your armpits is a quick-win for both men and women. This will reduce sweat build up, and so reduce smells.
You’ll immediately make your armpits cooler by removing hair. You will also allow the sweat to move away faster, giving a larger area for it to get evaporated away. Without the hot, damp, hairy recesses those microbes will not have a chance to get a foothold. This can help to reduce the smells.
A final benefit is that your anti-perspirant will be able to find the ducts to block easily. You will not be wasting 2/3rds of each application simply coating your hairs.
Pads: Discreet absorbent pads with sticky-tape on one side are readily available. These are designed to stick to your clothing, and simply soak up the sweat. These are perfect for use under clothing, and there is no reason anyone should know about them.
Showering Daily: This will be obvious and natural to 95% of you. For the other 5%; please, start this habit right away! Not only will you feel fresher, showering will prevent the build-up of our friends’ Staphylococcus Hominins and Corynebacterium.
Sweat, Food and Drink
Apocrine sweat cells get rid of salts, fats, acids, ammonia and nitrates. One of the key routes for those nasty substances to get in is via eating processed foods. These are so bad for us in general, that sweat is only a minor consideration. If your diet includes high processed sugar levels, trans fats, preservatives, flavour enhancers and other unnatural substances, then I don’t blame your sweat glands for working overtime to get rid of these things!
Busy lives mean that changing diet overnight is hard. There is no reason not to kick out the worst offenders, and to work on a clean eating regime slowly and surely.
Reducing ready meals, fast food, sugary drinks (including the sugar nightmare that is cartons of fruit juice!) and chocolate (candy) bars is a quick win that will leave you feeling better as well as sweating less.
Caffeine: This is a personal weakness of mine, I love coffee – preferably several times a day! This has a causal relationship with sweating. First as a stimulant to your nervous system. Second, warm beverages will naturally increase your core temperature.
Alcohol: There are primary and secondary links between alcohol and sweating. This causes blood vessels to dilate, raising your skin temperature and triggering a regular sweat response. High sugar levels in many alcoholic drinks also triggers insulin release – a secondary sweat trigger. For those who are dependent on alcohol, withdrawal symptoms also include increased sweat rates.
Extreme Interventions – Prescriptions, Botox and Surgery
I covered prescription drugs such as Anticholinergics in the ‘medical’ section above. These are effective for many people. Side-effects make them less suitable for general use. The balance between hyperhidrosis and the side effects is one thing – suffering side-effects just to reduce normal sweating is less desirable.
Botox is a poison (botulinium), which is usually used for cosmetic reasons on the face. It disables the mechanism which controls muscles, creating local ‘flaccid paralysis’. Lines and wrinkles associated with aging can be reduced.
Botox has another use, reducing sweat.
The mechanism by which botox stops muscles working uses acetylcholine. This is the same neurotransmitter which triggers the apocrine sweat glands. Your body will be telling your glands to sweat away, though they will never receive the chemical message. The effects of Botox are not permanent, the effects will wear off after 6 months.
Surgery is an extreme solution. It is only used when all the other options have been shown ineffective. There are two broad types. First, sweat glands can be scraped away. This involves an incision (primarily in the armpit). Laser treatments can be used after the incision to remove the glands. Local anaesthetic can be used for this type of surgery.
The second type of surgery involves cutting the nerves which link the brain to the sweat glands. This is more common in face and hand hyperhidrosis. By stopping the nerve signals, the sweat response is not triggered. Compensatory sweating can occur in other areas after this type of intervention.
Section 5 – Sweaty Facts, Figures and Fun!
If you made it this far, you’ll already be an expert on the mechanisms, causes and reduction strategies for sweating. This next part will add some entertainment to the mix. You’ll find 10 entertaining facts about sweat from sport, history and the animal kingdom.
#1 – The first deodorant was called Mum, this was created at the end of the 1800’s by Edna Murphey in Philadelphia. It would be 50 years before anti-perspirant followed. This was patented in 1941, by Jules Montenier and sold under the brand name ‘Stopette’.
#2 – Hippos sweat an oily red substance, known as ‘blood sweat’. This has been found to have anti-microbial properties.
#3 – Like many animals, humans produce chemicals known as ‘pheromones’ which affect the behaviour of the opposite sex. Research is at early stages concerning the mechanisms of how these work. This has not stopped many scammers selling sprays which are supposed to make you ‘irresistible’.
#4 – Hooved animals including Horses and Donkeys only have Apocrine sweat glands, these are their primary cooling mechanism. Non-primate animals only have sweat glands in their palms and soles of their feet. These are designed to aid escape, and not for cooling.
#5 – The fitter you are, the more you sweat. This makes sense, those who can use their natural cooling mechanism to good effect have an advantage in performance. While men sweat more than women on average, this is not as marked a difference as some headlines make out.
#6 – While replacing fluids during endurance activities like marathon running is important, this can also be dangerous. Hyponatremia, is a condition brought about by lack of salt. This can lead to disorientation and can even be fatal. While isotonic sports drinks help, it may still be possible to drink too much. Check out specialist advice, and if possible do a sweat test before you run. (guardian link.
No Panting Please!
#7 – While sweat may be embarrassing for many people, at least we don’t share a primary cooling system with other animals. Imagine if you needed to stop half way through a workout for a good pant!
#8 – One of the sweatiest contests ever held was the ‘Sauna World Championships’, which was held yearly in Finland from 1999 to 2010. Strongly opposed by the Finnish Sauna Association, this contest saw opponents sweating it out in 110c temperatures. This was stopped in 2010, following the death of a competitor, Russian Vladimir Ladyzhensky – and the hospitalisation of his Finnish opponent.
#9 – You have a staggering number of (mostly eccrine) sweat glands. Each person has between 2 and 4 million. This number is small compared to the number of microbes living on your skin. An average person plays host to 10 bacteria for every cell, that number is in the trillions!
#10 – Looking for love? Parties in Los Angeles and New York allow you to sniff out your perfect mate. You’ll be blindfolded, and sniff your way through potential matches speed-dating style. Check out this article from the Guardian for more.
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