B.O. for Beginners: Why the Whiff

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Tuesday, July 18, 2006

It's not your fault that you stink when you sweat. Your skin is one big petri dish teeming with bacteria. You wash most of them off when you take a thorough, soapy shower. But once you're out of the stall, microbe colonies start to repopulate.

Your skin is also home to millions of sweat glands: Eccrine glands, located over almost all of your body, especially your palms and the soles of your feet, secrete a mixture of salt and water when your autonomic nervous system signals that you're hot. The liquid they produce cools you down as it evaporates from the skin's surface. Apocrine glands, which kick in at puberty and are concentrated in your pits, crotch and scalp, secrete more complicated substances.

Physical stress causes more eccrine-gland secretion, while emotional stress is more linked to apocrine-gland sweat. Some medications and spicy foods can make you sweat, too.

Sweat-gland secretions themselves don't smell bad. But when bacteria (which also smell just fine) that are immersed in the sweat (they thrive in moist environments) dine on the fat- and protein-filled apocrine secretions, they produce foul-smelling excretions of their own.

Which is to say: The scent we know as B.O. is basically . . . bacteria passing gas.

As many as 30 chemical components of body odor have been identified. The hallmark chemical, according to Old Spice sweat expert Jay Gooch, is 3-methyl-2-hexenoic acid. "That's the one that, if you put it in a jar, you'd smell it and say, 'Ooh, that's B.O.,' " he says.

Gooch and George Preti, a body-odor expert at the Monell Chemical Senses Center in Philadelphia (who says it was his lab that discovered that B.O. acid in 1991), offer these tips for beating back B.O.:

· Start your day by bathing thoroughly. Soap kills bacteria, and water washes them away. Anti-bacterial soap keeps bacteria away longer than regular soap. And it goes without saying that you need to shower up again after your workout, right?

· Use an antiperspirant -- which plugs pores (often with aluminum compounds) so water and bacteria-chow can't get out. Or use deodorant, which suppresses bacteria growth and adds a pleasant scent. Most antiperspirants include deodorants, but not the other way around.

· Wash your gym clothes after every use, and wash them well. Preti suggests giving them a long soak in hot soapy water before laundering, as those smelly organic compounds cling tenaciously to fabric. Preti maintains that he actually practices what he preaches here.

-- Jennifer Huget


© 2006 The Washington Post Company

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