SWEAT is a clear, salty liquid produced by glands in your skin. Sweating is your body’s way of cooling you down. When your body senses that it is overheating, it begins sweating to control its temperature.

By promoting heat loss through evaporation, sweat helps to regulate your body temperature. The composition of sweat is dependent on which gland secretes the sweat. There are two main types of sweat glands — eccrine and apocrine.

Eccrine sweat glands are mostly concentrated on the palms, soles, forehead, and armpit, but cover your entire body. They open directly onto the surface of the skin. Eccrine sweat consists predominantly of water with small amounts of salt protein, urea, and ammonia.

Apocrine glands are larger and open into hair follicles instead of onto the skin surface. They are mostly located on the armpits, groin, breast area, face, and scalp. Although present from birth, they do not begin to secrete until puberty. They secrete a more viscous, odorous product and are the ones most often associated with body odour.

Apart from helping you to cool down, there are other reasons why your body starts producing sweat. When the body is reacting to an emotion such as anxiety, stress or excitement, sweat is released from the apocrine glands.

Causes of body odour

You may notice that odour mostly comes from your armpits. This is because the apocrine glands produce the bacteria that break down your sweat into fatty acids. Apocrine sweat by itself does not have an odour, but when the bacteria that lives on your skin mixes with apocrine secretions, it can produce an odour. This odour can change due to emotions, hormones, foods, infection, medications, age and underlying diseases.

Effect of foods

Spicy foods can stimulate your sweat glands by tricking your brain into thinking that your body temperature is increasing. This in turn triggers sweat production. Additionally, food allergies and intolerances can cause sweating while eating. Some people experience “meat sweats” which occur when they eat too much meat. What happens is that their metabolism spends so much energy breaking down the meat that their body temperature goes up.

In addition to stimulating sweat, foods can also affect how you smell when you sweat. Garlic, onions and cruciferous vegetables like cabbage, cauliflower and broccoli can affect the body odour due to the presence of sulphur compounds. These compounds are absorbed in the body and secreted through sweat. They then interact with the bacteria on your skin, causing a foul-smelling odour.

While some vegetables may cause a certain smell, a 2006 study, published in the Journal Chemical Senses, found that a vegetarian’s body odour is more attractive than that of a carnivore. The study included 30 women who sniffed and judged armpit pads that were worn by 17 male odour donors. The researchers discovered that men on a non-meat diet had a more attractive, pleasant, and less intense smell, compared to those who ate red meat.

The consumption of large amounts of alcohol can speed up your heart rate and dilate (open) blood vessels. This reaction, in turn, tricks your body into thinking it needs to cool itself down by sweating.

Body odour can change

The increase in various hormones during puberty makes the sweat glands more active resulting in the production of more sweat in sweaty areas like the armpits and the feet. This increase in sweat production contributes to conditions that give rise to an increase in body odour from smelly armpits and feet.

For older people, the change in body odour is likely due to an increase in levels of a compound called two-nonenal. This compound has a greasy and grassy odour. It is noteworthy that while people recognise older adults as smelling different, they do not necessarily consider it an unpleasant smell.

Causes of yellow underarm stains

Sweat is colourless. However, you may have noticed that some people experience yellow stains under the arms of white shirts or on white sheets. This is due to a chemical reaction between sweat and antiperspirant or clothes. Aluminium, an active ingredient in many antiperspirants, mixes with the salt in sweat and leads to yellow stains.

Salty sweaters

Some people sweat out more salt than others. You can tell if you are a salty sweater if your eyes sting when sweat drips into it, if an open cut burns when you sweat, or you taste your sweat. This may be related to your diet and consumption of water.

Sweating disorders

Hyperhidrosis is a medical condition that causes someone to sweat more than the average person. This sweating is not always related to heat or exercise. Medical conditions like diabetes mellitus and Parkinson’s disease can cause hyperhidrosis. In some cases, there is a genetic link.

People with hypohydrosis sweat too little. While genetics factor into this, medication to treat nerve damage and dehydration can also cause this condition.

Trimethylaminuria is a genetic sweating disorder that causes sweat to smell like rotting fish.

Happiness and sweat

Research has demonstrated that you can produce a certain odour that indicates happiness. This odour is detectable by others, stimulating a feeling of happiness in them as well.

Dr Jacqueline E Campbell is a family physician, and radio show host. She is the author of the book A Patient’s Guide to the Treatment of Diabetes Mellitus.

Email her at drjcampbell14@yahoo.com or follow her on IG: dr.jcampbell