The Science of Sweating



What Happens Inside When You Start to Sweat?

Very few animals sweat. In fact, alongside humans and other primates, horses and hippos are the only others. Some other animals, for example dogs, have a small number of sweat glands in their paws. Sweating evolved to perform two key functions. First, it is our primary cooling mechanism. Second, it flushes out toxins from the body. These include nitrates and ammonia.

While reducing sweat is part of the daily routine for most people – the mechanisms behind this are not so well known. This article explains, in simple terms, how sweating works. You’ll find out about two distinct types of sweat gland, the neural mechanisms which trigger the sweat response – and why some people sweat more than others below.

After the hard facts, there is a short section covering some practical tips for reducing visible sweat.

What Triggers Sweating?

The short version of ‘get too hot, you sweat’ only touches on how this complex system works.

Skin temperature and core temperature both have a role. This explains why we can still sweat when running on a cold wintery day, or exercising in an air-conditioned gym. For most people that balance of core and skin temperature is the key to when the sweat response is triggered. To get the full picture, humidity, heart rate and your own fitness level need to be considered.

If you are physically fit, you’ll sweat sooner. This is a positive adaption; your body begins the cooling process when it feels your core temperature rising. This allows you to stay on that gym equipment for longer.

This response is started in an area of the brain known as the Hypothalamus. This is an older part of the brain, concerned with regulating many automatic processes such as body temperature and your heart rate. The release of the neurotransmitter Acetylcholine then travels to the cells. It triggers contraction, which forces out the stored sweat.

Two Types of Sweat Glands

Most sweat glands are known as Eccrine glands. These cover most your body, and have small, independent ducts leading to the surface of the skin. An average person will have 2 to 3 million Eccrine sweat cells. The sweat which comes from these cells is thin and watery. It is primarily water, with a little salt mixed in.

The other type of sweat cell is more localised. Apocrine cells are found primarily in your armpits, with a smaller number in the genital region. These cells share ducts with hairs, and are indirectly responsible for smelly sweat. Sweating from Apocrine glands can be triggered by adrenaline, as well as via the usual cooling mechanisms.

Smells do not occur directly. Apocrine cells discharge oily sweat. This includes fatty acids, proteins, nitrates and ammonia – as well as water. Microbes love this mix. The especially love the conditions in your armpits (warm and damp, often with hairs to cling to). The smell we associate with sweating is the result of microbes feasting on your sweat.

Some People Naturally Sweat More

There are huge individual differences in how much we sweat. In fact, genetic propensity is the single biggest determinant. There are other factors. Drinking alcohol increases sweat responses, as does consuming processed foods – especially if these contain excess salts, hydrogenated oils or chemical preservatives. Obesity increases sweating indirectly, making it harder to get active and increasing core temperature when performing simple tasks. Finally, environmental conditions – including heat and humidity – affect our propensity to sweat.

Sweating can become a medical problem. Hyperhidrosis is the term for sweating which gets so extreme that doctors need to intervene. This is often localised, for example sweaty hands or forehead. Most people who report hyperhidrosis symptoms are within the ‘normal’ range – though may well have a genuine concern about their sweat levels.

How Does Science Suggest Reducing Sweat?

Most people’s go-to solution is anti-perspirant. This is effective, and works by physically blocking the sweat ducts. The most common chemicals used are Aluminium Chlorohydrate and Aluminium-Zirconium Tetrachlorohydrate. These form a plug at the top of the sweat ducts of Apocrine glands. Over time these naturally come out, which is why we apply this every day. Usually, antiperspirants include alcohol. This kills off the microbes – reducing the chance of getting smelly.

A real boost to the effectiveness of underarm antiperspirants is to remove the hair. Women have known about this for years. Men with excess sweat can cool things down, and allow the chemicals to reach their target at the same time this way too.

Covering up sweat is simple if you know what to wear. Pick clothing which is navy blue, black or plain white to make sweat less visible. An undershirt works well, though does have the adverse effect of increasing your temperature. Pads can be bought very cheaply, and will discreetly soak up excess moisture.

Healthy eating, reducing alcohol intake and drinking water rather than soda all contribute.

If you still have serious issues with sweating, then you should consult with a medical professional. There are more drastic solutions. These include the use of Botox, which stops the neurological signals from reaching the sweat glands. Surgery to remove the glands, or cut the nerves which service them is the final option.