Understanding how we sweat
Every day we produce on average one litre of sweat. Our skin contains millions of glands, and it is some of these that produce sweat. When we are hot, active, nervous or stressed, our sweat glands are stimulated to produce more sweat. As sweat evaporates from our skin, it absorbs heat energy from our body and so cools us down.
We have between 25,000 and 50,000 sweat glands in our armpits alone, although this is actually only a small percentage of our total. But the sweat is more likely to get trapped under our arms and can't escape and so it is more noticeable here. This is when bacteria start to feed off the sweat and create body odour. Sweat itself doesn't actually smell at all.
There are two types of sweat glands on our bodies - eccrine and apocrine. The former are all over our body and control temperature. The latter are concentrated in certain areas, such as the armpits, and can be triggered by stress. This 'emotional' sweating can be a problem because about double the amount of moisture is released. This means more for the bacteria to feed on and so greater body odour.
The difference between anti-perspirants and deodorants and how they work
Sweat itself does not have an odour, but it contains proteins and fatty acids which bacteria on the skin ‘feed’ on. It is the bacterial by-products that produce the bad odour. Bacteria are always present on our skin, and sweat is more likely to get trapped under our arms and can't escape and so it is more noticeable here. This is why deodorants and antiperspirants are usually applied to the underarms.
Antiperspirants help prevent perspiration by dissolving in sweat and creating a thin coating of gel that covers the sweat glands. This coating reduces the amount of sweat released onto the surface of the skin and therefore reduces the risk of odour by taking away the sweat that bacteria work on which results in odour.
Deodorants don’t reduce the amount of sweat released onto the surface of the skin. Instead, they can be used under the arm or all over the body (as body sprays) to control body odour. Deodorants use ingredients such as alcohol and antimicrobials to kill bacteria and include fragrance to mask bad smells.
Some deodorants have been developed so that the fragrance is released over a long period of time. Fragrance is enclosed in tiny micro-spheres of corn starch which break open, releasing a smell when saturated with sweat. Smaller micro-spheres will release fragrance straight away; larger ones will break down more slowly.
Products have also been specifically designed to reduce white marks. For example, the product is developed to affect the way that light is bounced off the skin so that there is less visible white powder.
