How Body Odor Works

Man with body odor
Body odor affects all of us. But what makes our bodies smell in the first place?

Raise your hand if you've ever been on a bus or in any other cramped quarters next to someone who just smelled bad. On second thought, never mind.

The fact is, all mammals smell. In the wild, the odors produced by animals help them identify each other and choose healthy mates. In humans, one of the first ways newborns bond with their mothers is through their sense of smell. Studies have shown that little ones find the scent of their mother more comforting than that of any other woman, while other research shows that our individual scents are as unique as our fingerprints [sources: The New York Times, Thompson]. The U.S. Department of Homeland Security is even conducting experiments to not only identify people through their odor types but also figure out when they're lying.


Even though shouts of "You've got B.O.!" at a school playground might cause the scientifically minded to reply, "Of course, we all do!" the fact remains that when people talk about body odor they're speaking of the unpleasant, sometimes eye-watering kind found in a football team's locker room at game's end. Or at far too many convention halls.

So what is it that causes the body to smell like an unwashed elephant from time to time? The answer that immediately springs to mind is, of course, sweat. But that's only a part of the story. Sweat, on its own, is odorless. The smell that betrays us on first dates and job interviews is actually a product of digestion. And it's not from our stomachs.


The Cause of Body Odor

Apocrine sweat gland
Eccrine sweat gland

Sweat is produced by two different glands. Eccrine glands cover most of the body and produce sweat primarily consisting of electrolytes and water, which cools the body when it evaporates from the skin.

Apocrine glands are found in the groin, hands, feet and underarms. These glands produce sweat that contains proteins and fatty acids, which makes the perspiration thicker and milky or yellowish in color. This is where the sweat stains you see on light-colored shirts come from. While eccrine glands are activated as part of the body's cooling system, apocrine glands can produce sweat when the body is experiencing anxiety, nervousness or stress.


When it first emerges on our skin, sweat is just a fluid without an odor. However, the bacteria on our bodies are particularly attracted to the proteins in apocrine sweat which they eat, digest and expel as highly-aromatic fatty acids. These include the notorious (and notoriously named) (E)-3-methyl-2-hexenoic acid. The process typically takes about an hour.

It doesn't help that the apocrine glands are found in the moist, dark areas of the body -- exactly the neighborhoods in which odor-producing bacteria like micrococci and staphylococci enjoy living. When we wrap our feet in socks and leather shoes, we not only create a haven for bacteria, but for fungi as well, which is why our foot odor can be particularly troublesome and different in character from underarm smells.

Our apocrine glands do not become active until we reach puberty, which is why babies smell sweet -- teenagers, not so much.

Not only are there differences between first-graders and high school seniors in terms of body odor, there are also disparities between men and women and even between members of different races, as we'll see in the next section.


Degrees of Body Odor

Because it's the sweat produced by apocrine glands that odor-causing bacteria enjoy eating, it follows that the fewer of these glands a person has, the less offending odor he or she produces. That's why pre-pubescent teens whose apocrine glands haven't yet been activated don't tend to have strong body odor. It's also why Asians, who have the fewest apocrine glands of any race, are known as the least-stinky people on Earth [source: Lynn]. In fact, body odor has been rumoured to be enough of a reason to keep Japanese men out of military service [source: Burr].

In the B.O. Olympics, people of European or African ancestry hold all the medals. And among those, the men take the gold. That's because women are more efficient regulators of their body temperatures than men and sweat less, needing body temperature that's a degree higher before they begin to perspire. One theory why this is so is because men carry greater degrees of fat and muscle which keeps their cores warm. Without this extra thickness, women have evolved to be able to pull heat-carrying blood in toward their cores as a preservation mechanism. Men also have a higher degree of testosterone which can up the production of apocrine sweat.


All that extra manly sweat leads to extra stink, which is a double-edged sword for women. According to a study conducted at the Monell Center in Philadelphia, women were more adept at picking up clues in male underarm odors which helps them determine biologically relevant data about their subjects such as the health of their immune systems. Yet the female nose was also harder to trick when it came to disguising male aroma beneath other fragrances [source: Wysocki].

Not only do individual races and sexes produce body odors differently, there's a disparity in the way people throughout history and in various societies perceive human fumes. For example, members of a tribe in New Guinea say goodbye to each other by placing their hands under each other's armpits so that they can take a little of their tribemates home. Historically, in parts of the Austrian Tyrol, young men would dance with a handkerchief under their arms and then wave it under the nose of a woman in whom they were interested. In Elizabethan times, lovers would stay "in touch" by exchanging peeled apples which had been soaked in armpit sweat before the lovebirds split company.

The food eaten in various cultures can also have an impact on the personal incense released into the air through our eccrine glands. That's why Indian body odor can have notes of curry, and members of cultures that consume copious amounts of garlic can begin to smell like "stinking roses" themselves. Other foods that can impact body odor include red meat, onions and asparagus. Of course foods that make the body sweat such as caffeine, chilis and alcohol can also contribute to the pungent perfume that is you.

So what to do about all of this Eau de Monsieur e Madame? Find out in the next section.


Methods of Dealing With Body Odor

Most body odor can be banished with simple hygiene techniques.

Scientists postulate that one reason our unpleasant smells come from hair-packed areas on our bodies is because at one time, just like animals, humans used scent to broadcast the pheromones in our sweat to attract mates. When that scent got tangled in our hair, it stuck around longer.


Fortunately, we now use a host of other scents to make ourselves appealing to the opposite sex, but that doesn't mean odors still don't get trapped in our body hair. So one simple solution to persistent B.O. is to trim the hair in odor-producing regions like the underarms and groin.

Another is bathing. Because it takes bacteria about an hour to digest the proteins in our apocrine sweat, the sooner we wash it away, the less chance there will be for mini-stink factories to begin churning out their exhaust. In addition to bathing our bodies, sweaty clothes should be washed frequently as well.

Eliminating the odor-producing foods mentioned in the previous section can help, as can trying any of the following natural remedies:

  • Boric Acid -- It might sound like something you wouldn't want anywhere near your body, but it is actually a weak acid that can help eliminate underarm odor when dusted in that area.
  • Apple Cider Vinegar, Alcohol, Witch Hazel -- Some people have had success swabbing the underarms with these inexpensive and readily available solutions.
  • Baking Soda -- It works in your refrigerator to absorb odors and can do the same when dusted on problem areas on your body.
  • Rosemary Oil -- Diluting 8 to 10 drops in an ounce of water and then applying under the arms may also be effective.
  • Chlorophyll -- Many natural medicine practitioners claim that taking this plant material internally in pill form can reduce your external whiffiness.

If you're more inclined to turn to the pharmacy than the natural market for cures, then read on to find out more about deodorants and antiperspirants.


Antiperspirants and Deodorants

In 1888, a product called Mum hit the markets and kicked off the personal deodorant industry that is in full flourish today. Mum was the first commercially trademarked antiperspirant in the United States but it was messy and hard to apply. Things improved by the turn of the century with stick-style deodorants and later aerosols, which eventually fell out of favor due to their role in depleting the ozone layer.

Today, Americans spend over $2 billion a year tackling their BO [source: Park].


There are two primary ways to minimize axillary, or armpit, odor: antiperspirants and deodorants. Antiperspirants work because they contain one or more chemicals like aluminum chloride or hydroxybromide. When microscopic portions of the aluminum enter the skin, they take water with them. This causes sweat ducts to swell and eventually close, preventing them from delivering their contents to the skin's surface. Less sweat means less breeding ground for bacteria, which means less odor. Antiperspirants tend not to be as effective when applied immediately after a shower, as the body is still moist, which may keep the substances from sticking to the skin. The strongest antiperspirants available contain 12 percent aluminum chloride and include Certain Dri and Xerac. If they don't get the job done, stronger preparations containing up to 20 percent aluminum chloride are available by prescription.

If you don't sweat to excess, a deodorant might be sufficient to muffle your malodor. Deodorants don't block the body's natural sweating mechanisms. Instead, they use a variety of chemicals like triclosan, an antibacterial agent that makes the environment under your arms inhospitable to the critters that foul your personal airspace.

For people who like to go natural -- but not au naturale in terms of odor protection -- there are deodorants like Tom's of Maine that are free from synthetic chemicals. When evaluating such products, it can be helpful to look for ingredients such as chamomile, lemongrass, sage, licorice, goldenseal, tea-tree oil or coriander -- which have either anti-odor or antibacterial properties.

Another natural option is a mineral crystal deodorant that makes the underarm environment too salty for odor-causing bacteria to thrive. Because everyone's body chemistry is different, it may take a bit of experimentation to find a natural deodorant that works for you but the science of making the skin's surface unfriendly to bacteria is sound, and thousands of people use these products successfully every day.

Still having trouble with body odor? It might be time to consider if a medical condition is the cause, as we do in the next section.


When is Body Odor a Problem?

As we've seen, despite our use of sprays, sticks and powders, our bodies smell. It's normal. And, even though the scientific name for body odor -- bromhidrosis -- sounds like something to be concerned about, it can usually be handled by the methods previously discussed. But sometimes, when the body gives off a strong odor, it can be a sign that something is medically amiss.

Diabetes can give the breath a fruity smell and the body a distinctive odor akin to nail polish remover due to a condition known as ketoacidosis. An unusual body odor can also be a sign of liver or kidney distress. Some infections also produce foul smells; for example, a mouth abscess could cause bad breath, while a vaginal yeast infection would have an accompanying odor. Scientists have even developed a method for identifying lung cancer through breath analysis [source: Alvarez].


Occasionally, a strong body odor can be a sign of a metabolic disorder and is usually discovered in childhood. Individuals suffering from primary trimethylaminuria lack the ability to metabolize a substance known as TMA and emit a smell that has given the disease its more common name: fish-odor syndrome [source: Reuters]. Children who suffer from maple-syrup urine disease lack an enzyme to break down certain amino acids and may smell like the disease's namesake, while adults with the condition have urine that smells like burnt sugar. People afflicted with phenylketunuria are unable to break down the protein phenylalanine and can emit a musty or barn-like smell.

Another disease that is linked to excessive body odor is hyperhidrosis, a condition marked by abnormally high perspiration -- even if the individual experiencing it is cool or at rest. If prescription antiperspirants aren't enough to bring the condition under control, more severe methods may be employed. These include anti-sweating drugs; iontophoresis, the use of an electrical current that disables sweat glands; botox injections in the armpits that temporarily block sweat-stimulating nerves; and an endoscopic surgery procedure known as ETS where the nerves that cause the excessive sweating are removed.

Metabolic disorders and hyperhidrosis affect only a small portion of the population, so chances are good that the musk you make is simply your unique odor type and not a cause for alarm. However, if you try normal odor-obliteration techniques with no results, it might be time to see your doctor.


Lots More Information

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