SOME people get smelly by the end of the day, no matter how diligently they wash and deodorise in the morning. But soon the bugs that cause the problem could be kept at bay by deodorants that starve them of a crucial nutrient.
Fresh sweat has no odour. It鈥檚 the vast colonies of bacteria that feed on it, especially in warm, damp armpits, that produce malodorous molecules. Most underarm deodorants use alcohol to kill the bacteria, but some inevitably survive and multiply throughout the day.
A few manufacturers add antibacterial chemicals to try to keep the deodorant working longer. But Andrew Landa and his colleagues at the Unilever Research and Development Laboratory near Liverpool have taken a different approach. Sweat contains trace amounts of iron, which most bacteria need in order to multiply. So Landa and his team created a deodorant containing DTPA (diethylenetriaminepenta-acetic acid), a chemical that binds to iron so the bacteria can鈥檛 use it.
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But that alone isn鈥檛 enough. Some of the iron in sweat is combined with iron-carrying proteins, and bacteria that can break down the proteins will still get the iron they need. To prevent this the researchers added a second ingredient, called butylated hydroxytoluene (BHT), which releases iron from the proteins so that it too can be captured by DTPA.
When a deodorant containing this combination was tested on 50 volunteers over two weeks, it reduced bacterial numbers by 90 per cent compared with a standard deodorant, Landa told the American Society for Microbiology meeting in Salt Lake City this week. More to the point, it reduced BO. This was verified in double-blind tests, conducted by Unilever鈥檚 鈥渆xpert assessors鈥�, who had the unenviable job of assessing how people鈥檚 armpits smelt 5 hours and 24 hours after the deodorant was applied.
Landa won鈥檛 say whether Unilever is planning to market a deodorant that contains the iron-trapping chemicals. But the company has applied for patents in Europe and the US.