Sweating

This guide discusses all aspects of excessive sweating but it may be useful to know what sweating is and why it is a normal part of being human. So, why do we sweat and why do we need to sweat?

Anatomy of sweat

Within our skin lie tiny, cylindrical structures called ‘sweat glands’which are responsible for the process we know as sweating. These glands form part of the sympathetic nervous system which enables the body to remain in balance as a response to any external changes, e.g. the weather.

This includes maintaining a core body temperature. There are two types of sweat glands which are:

• Apocrine sweat glands
• Eccrine sweat glands

Apocrine sweat glands

These are located in certain areas of the body – the armpits, genital/anal and areola (circular coloured area) of the nipples, external ear canal and around the navel (belly button).

They have a coiled, tubular appearance and from puberty, produce a thick, greasy looking sweat around the hair follicles. This sweat may interact with bacteria causing a strong odour.

This type of sweat can contain pheromones - a type of chemical which attracts the opposite sex.

Eccrine sweat glands

These are smaller in size than apocrine glands but they are also tightly coiled, tubular shaped glands which produce a clear, watery type of sweat. These glands are present in the dermis (skin) and are found in nearly all areas of the body apart from the lips, clitoris and tip of the penis. The density of these glands depends on their location within the body: the highest density of eccrine glands is found on the scalp, soles of the feet and the palms of the hands. The sweat secreted by these glands is mostly water based although it also contains electrolytes (minerals) which gives it a ‘salty’ taste. It also contains a small quantity of urea.

Electrolytes help to keep fluid levels in balance and ensure that organs such as the heart function as normal in the body. Examples of these include chloride, potassium, sodium and calcium and are present within the blood, tissues and bodily fluids, e.g. urine.

Note: these salts give sweat its white colour which you may have noticed if you engage in endurance sports such as triathlons or marathon running. Many athletes find that they have salt deposits on their face and bodies and/or clothing if they have participated in these events, especially in hot weather. The eccrine glands have three functions which include:

• Thermal regulation: they help to cool the skin and lower body temperature.
• Excretion: they remove water and electrolytes
• Protection: they protect the surface of the skin from bacteria and other potentially dangerous organisms.

How much sweat do we produce?

That depends upon the sex of the person, how many eccrine glands they have and the size of the openings on the surface of the skin. Basically, a person can lose more than 3 litres of sweat in an hour -if their eccrine glands are working at full capacity. The danger with this is that essential fluids and electrolytes may be lost which in some cases, can be life threatening.

Sweating and the sexes

You may be familiar with this phrase:

“Horses sweat, men perspire but ladies glow” What does it mean? It means that all of us sweat, whether human or animal. We use different names to describe it but at the end of the day it is an essential function needed for our survival. This witty saying refers to the fact that at one time, sweating was considered unladylike for women and was something that only men experienced.

But women do sweat although not to the same extent as men. Men produce greater amounts of sweat than women and at a much quicker rate especially during exercise.

We are all individuals when it comes to sweating and one person will sweat more than another. But gender does play a part and so does evolution.

Evolution and sweating

It appears to be the case that men evolved to sweat more than women as they were usually more physically active and needed to reduce their body temperature when hunting. This acted as a strategy for greater efficiency whilst being physically active.

Whereas women tended to be less active than men and as a result of this evolved to sweat less than men. This may be a type of survival strategy in that it enables them to exist in a hot environment.

But there are additional risks for women as a result of this. Their smaller body size and weight mean that they are less efficient at cooling down than men which increases the risk of dehydration. This also increases the risk of heat stroke/heat exhaustion which can be life threatening.

The mechanism of sweating

Sweating is regulated from an area within the hypothalamus (region of the brain which controls a range of processes including body temperature). This area contains neurons which are sensitive to changes in body temperature. Temperature receptors within the skin affect the function of the hypothalamus for example a rise in temperature lowers the set point for sweating. This response is greater in situations where the core temperature of the body is higher than those for an increase in normal skin temperature.

Sweating reduces the core temperature of the body: sweat then evaporates which reduces the temperature of the skin surface.

We have mentioned about the role of the sympathetic nervous system in regard to sweating but over-activity in this area may be a cause of excessive sweating (hyperhidrosis).

Find out more in our what is excessive sweating? section.

The importance of sweat and body temperature

Sweating is a natural function of the human body which helps to regulate our core temperature. It occurs when body temperature rises either due to external factors, e.g. a hot day or from strenuous exercise and helps to cool the body down. Fluid is lost through the skin through evaporation which has the effect of removing heat and reducing the temperature of the body. It also removes toxins from the skin but not to the extent which many people think it does. People often assume that sweating is the most important way of removing toxins from the body which is reflected in the popularity of saunas and steam rooms. Many people use these as a way of allowing toxins to be ‘sweated out’ of the skin and they are effective at doing so but there are other options as well.

Physical and emotional causes of sweating

People who are very fit tend to lose greater amounts of sweat than less fit people. Endurance athletes such as marathon runners can lose as much as 6 pints of sweat in an hour which is why it is important that they drink at regular intervals during a race.

Exercise is one cause of sweating but sweat is lost from the body in two ways:

• Physical exercise
• Emotional stress, e.g. before a job interview

Physical exercise causes sweat to be lost from the entire body whereas emotional stress restricts this to certain areas of the body, for example the palms of the hands. The amount of sweat also varies according to the environment. If you move from cold surroundings to a warm climate then you will notice that your ‘sweating mechanism’ has adapted to this change. This acclimatisation means that you will lose a greater volume of sweat which includes electrolytes.

Conversely, if you move to a cold climate and are relatively static then you will sweat less and only lose a small amount of electrolytes, e.g. salt. The amount of salt lost depends upon your body weight and how well (or not) you have acclimatised.

You sweat as a means of regulating your core temperature. If you did not then you would run the risk of overheating which is potentially fatal especially in hot weather or during exercise.