The taming of the stink

Body odour explained

Sweat doesn’t have a smell: it is the bacteria that live naturally on our skin and in our sweat glands that cause body odour. We all have around 1000 different species of bacteria on us at all times, with millions of individual bacterium per square centimetre. These bacteria break down fats and acids in sweat – which the apocrine glands produce – creating whiffy waste products. These unpleasant smelling molecules include propanoic acid, which gives off a vinegary smell, 3-methylhex-2-enoic acid, which smells like goat, and 3-methyl-3-sulfanylhexan-1-ol, which smells like onions.

No one’s sweat is the same. Our diets change its composition, with certain foods creating particularly pungent odours. Genetics also play a role – around 2% of the UK population has a rare form of the gene ABCC11 which means they don’t produce body odour at all.

Sweat prevention

Now that we know what’s causing the smell, how best do you deal with it? Typically, we use a spray, where the active ingredients dissolve in a pressurised solvent, which then evaporates to leave the ingredients on the skin; or a stick, which uses a combination of waxes and oils to rub the ingredients where we want them.

If antiperspirants act at the source of body odour, then deodorants tackle the result

Some products are called natural antiperspirants and usually include ingredients such as corn starch. In reality, these aren’t antiperspirants at all – they absorb sweat as it emerges, rather than blocking the gland. The best-known product of this type is talc, a mineral made of magnesium silicate, which absorbs water released in sweat. Professional sports people, such as gymnasts and weightlifters, often use talc to ensure they have a dry grip.

Neutralising unwanted smells

If antiperspirants act at the source of body odour, then deodorants tackle the result. Deodorants usually contain powerful, pleasant fragrances to mask a natural musk: essentially replacing one smell with another. Unlike perfumes, which aim to enhance a smell, deodorants use scent combinations to neutralise odours. But they can also contain compounds that target the bacteria more directly. The most controversial molecule of this type is the antimicrobial triclosan, which is banned in several countries (but not the UK). Triclosan works by making skin more acidic, creating an environment that stops bacteria from growing, preventing them from creating body odour.

The problem with its use is that our skin is a complicated ecosystem; if you get rid of all the natural bacteria, makng serious bacterial infections harder to treat. There are also concerns that triclosan use could contribute to increased antibiotic resistance, leaving serious bacterial infections harder to treat.

If you’re looking to battle your body odour, chemistry has you covered. But if your smell is still bothering you after using these products, remember that your internal chemistry can be a contributing factor. Changing your diet can also help cut down on any unwanted stink coming from under your arms.