Ahh puberty — the time of so many exciting changes to the body. Sure the girls get that more womanly figure and the guys start to develop more muscle and that manly voice but it's also the time for those other changes like acne, hormone swings and producing more sweat.

There are actually some scientists whose job it is to collect axillary secretions - that is - armpit sweat. Sounds like a great job worth stepping up for, eh? Well what these scientists are really after are the various chemicals that are in our sweat. Knowing the identity of these molecules is what helps these scientists come up with methods that help us to avoid sweating (not to mention those nasty arm pit sweat stains) and more importantly, smelling.

Smelly Sweat - Pee-ew!

Surprisingly, on its own, our sweat does not smell at all. It is the bacteria that live on our skin that produce these odours. Armpits are a very nourishing environment for some bacteria. There, they can convert odourless chemicals that we sweat out, into the smelly ones that we all recognize and want to avoid.

Did You Know?
Armpit hair increases surface area for the bacteria to act. More armpit hair means worse smells!

There are a number of compounds that have already been proven to be the culprits of B.O., but scientists are still trying to identify others. Two of the strongest smelling (and strangest named) structures found so far are (E)-3-methylhex-2-enoic acid and (S)-3-mercapto-3-methylhexan-1-ol (it's easier to just look at the picture).

Stopping B.O. in its Tracks

Alright, so you may not really care about what the chemicals are that cause B.O., you really just want to know how you can avoid them. Your two weapons are deodorants and antiperspirants...but what's the difference between them?

To clear up the confusion, deodorants are composed of antimicrobial agents that will kill the bacteria growing in our armpits that produce those nasty smells. If the bacteria are dead, then they cannot produce those smelly compounds. This doesn't stop us from actually sweating though, and we can still suffer from those embarrassing wet stains.

Did You Know?
Different compounds are produced depending on the reason you sweat; exercise sweat smells different than stress sweat.

Antiperspirants, on the other hand, have the intention of preventing us from sweating in the first place. These are much more commonly used, and generally more effective. If you don't sweat at all, how can you smell, right?

Antiperspirants contain aluminium ions (Al3+), which can come in many forms, including: aluminium chloride, aluminium chlorohydrate, and aluminium zirconium tricholorohydrex glycine.

Why would aluminium ions be added? Well, these ions can penetrate the cells in the pores of our armpits. As a result of the ions passing into the cells, the cells absorb a lot of water and swell up. Eventually, the cells swell up so much that the pores close, preventing the sweat from pouring out.

So what do you choose? Deodorant or antiperspirant? Many of the brands that you may choose will indeed contain chemicals that combat both smell (antibacterial agents) AND sweating (aluminium complexes).

Did You Know?
The same odour causing chemicals are found in both men and women.

Some brands also contain more natural ingredients like baking soda, to ward off the odour causing bacteria. Since these bacteria thrive in an acidic environment, the baking soda (a.k.a. NaHCO3 or sodium bicarbonate — a base) stops them from producing odours.

Regardless of the technique that you choose to use to avoid sweating - or at least the smell of it — it is important to recognize the amazing chemistry that is behind it all. It is also amazing to think that, after thousands of years of human existence, we still have not worked out the perfect formula to prevent this problem. Some chemists are at this moment collecting more sweat, and testing what makes it smell least bad. But that is probably a job best left to them.

Learn More!

How Stuff Works

http://health.howstuffworks.com/question627.htm

Chemistry Daily on Antiperspirant

http://www.chemistrydaily.com/chemistry/Antiperspirant

Reactive Reports:

http://www.reactivereports.com/41/41_1.html

Delicious Organics on Antiperspirants

http://www.deliciousorganics.com/Controversies/antiperspirant.htm

Psoriasis Café on Sweat

http://www.psoriasiscafe.org/sweat-works.htm

Troccaz M, Starkenmann C, Niclass Y, Van de Waa M, Clark A. 2004. 3-Methyl-3-sulfanylhexan-1-ol as a Major Descriptor for the Human

Axilla-Sweat Odour Profile. Chem. Biodiv. 1:1022-1035

Zeng, X-N, Leyden, JJ, Lawley, HJ, Sawano, K, Nohara, I, Preti, G. 1991. Analysis of characteristic odors from human male axillae. J. Chem. Ecol. 17:1469—1492.

Zeng X-N, Leyden JJ, Spielman AI, Preti G. 1996. Analysis of the characteristic human female axillary odors: qualitative comparison to males. J Chem Ecol. 22: 237-257.

David Dietrich has been a student his entire life - 24 straight years and counting... Presently he is working on his PhD in bio-organic chemistry at UBC in Vancouver. He hopes one day to experience life outside of school.

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