What is sweat?
Sweating is a body’s way of dealing with excessive heat — the water cools the skin and reduces body temperature. Exercise, over-stimulated nerves (anxiety, fright), fever, spicy food and external heat and humidity can all cause sweating.
There are, however, two different kinds of sweat produced by two different sweat glands. Eccrine sweat glands produce sweat containing mainly water and some salts (electrolytes). This sweat comes out of dedicated pores in the skin. Apocrine sweat glands produce a thicker, milky liquid containing proteins, ammonia and fatty acids. And this sweat comes out of hair follicles, rather than dedicated pores.
Where do we find sweat glands?
The adult human skin has several million sweat glands over almost the whole body, with high concentrations of eccrine sweat glands to be found on the forehead, palms, armpits and soles of the feet. Apocrine sweat glands are found in high concentrations in the armpits and around the anal-genital area.
Why does underarm sweat smell?
Sweat itself doesn’t smell – or at least not much. Rather, it’s the bacteria breaking down organic compounds in sweat that smell. The more ‘organic’ the sweat, the more bacteria, and the greater the smell. The apocrine sweat produced by our armpit sweat glands is rich in organic matter, and the warm, moist conditions are ideal for sweat-eating bacteria. Having hairy armpits increases the surface area for bacteria, which in turn increases the smell. Most underarm sweat is actually eccrine.
What’s the difference between antiperspirant and deodorant?
Antiperspirants reduce wetness; deodorants don’t reduce wetness, but rather mask or reduce the unpleasant odour associated with sweat.
How do they work?
Deodorants often contain anti-bacterial ingredients which help reduce bacteria ultimately responsible for making the smell. They may also contain perfumes which mask the smell. Antiperspirants contain aluminium compounds which appear to reduce sweating by temporarily plugging pores. Antiperspirant products often contain deodorising ingredients as well as antiperspirants.
Are there any ‘natural’ alternatives?
Despite the negligible risk, some people are concerned about the health effects of using aluminium products on their skin, and prefer to avoid them. Apart from aluminium-free deodorants (as opposed to antiperspirants) there are various ‘natural’ alternatives commercially available in health food shops and over the internet.
Deodorant crystals are a popular alternative. Their active ingredient is alum, usually in the form of either potassium aluminium sulphate or ammonium aluminium sulphate. So yes, they do contain a form of aluminium. However, companies claim that the aluminium is bonded to a molecule that’s too large to penetrate the skin. Alum is an astringent, which means it shrinks or constricts pores, and may help reduce perspiration. It may also have antibacterial properties.
A home-made deodorant can be made from equal parts of corn starch and sodium bicarbonate mixed with essential oils to reduce the activity of bacteria -- sage, thyme and cinnamon are all reported to be good deodorants, while sage is also recommended for its antiperspirant qualities.