Body Odor, often abbreviated as B.O., or bromhidrosis (also called bromidrosis, osmidrosis and ozochrotia) is the smell of bacteria growing on the body. These bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless. Body odor is associated with the hair, feet, groin (upper medial thigh), anus, skin in general, armpits, genitals, pubic hair, and mouth.

Body odor is largely influenced by major histocompatibility complex (MHC) molecules. These are genetically determined and play an important role in immunity of the organism. The vomeronasal organ contains cells sensitive to MHC molecules in a genotype-specific way. Experiments on animals and volunteers have shown that potential sexual partners tend to be perceived more attractive if their MHC composition is substantially different. This behavior pattern promotes variability of the immune system of individuals in the population, thus making the population more robust against new diseases.

A recent study suggests that body odor is genetically determined by a gene that also codes the type of earwax one has.East Asians evidently have a greater chance of having the 'dry' earwax type and reduced axial sweating and odor. This may be due to adaptation to colder climates.

Is Body Odor Normal?

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Jack is not the first (or last) teen to notice body odor. Bromhidrosis (another word for body odor) happens at puberty because of increasing hormones called androgens. These hormones are not active until puberty, which is why body odor wasn’t a problem when you were a kid.

While sweat itself is virtually odorless, bacteria use it as a breeding ground and multiply rapidly. What you smell is the bacteria multiplying on the surface of your skin. Sounds disgusting, doesn’t it? Chalk it up to an unpleasant fact of life!

When you work out or move around in the heat or sun, your body produces sweat. Sweating is the body’s way of regulating temperature. When sweat meets the bacteria on the surface of your skin, it produces an odor. That smell is what we call body odor (or B.O. for short).

Why Do My Feet Smell?

While body odor is usually associated with the armpits, bacteria can also produce odor in the groin, anus area, upper thighs, and feet, among other places. Thoroughly washing your skin with a wet washcloth and soap -- especially those areas prone to sweating -- can help prevent body odor.

Remember that smelly feet can also cause smelly shoes. Treating your shoes with an over-the-counter deodorizer can help. Also, wear thick, absorbent socks if you can.

How Do I Fight Body Odor?

If you want to be "odor-free," consider the following tips:

1. After washing with soap and completely drying, immediately apply an underarm antiperspirant. Remember, deodorants do not prevent sweating. They mainly mask the smell of the bacteria on your sweaty skin. Antiperspirants are chemical agents that reduce sweating. Many antiperspirant preparations also contain a deodorant, which helps to mask the smell. Check the product you use to make sure it contains an antiperspirant.
2. Keep your underarms dry. Bacteria have a hard time breeding in dry areas of the body.
3. Try a solution of hydrogen peroxide and water to fight body odor. Use one teaspoon of peroxide (3%) to one cup (8 ounces) of water. Wipe this on affected areas (underarm, feet, groin) with a washcloth. This may help destroy some of the bacteria that creates odor.
4. If sweat from working out is your No. 1 cause of body odor, wash your workout clothes often. Sweaty gym clothes are a bacteria-breeding ground.
5. Change your diet. Sometimes, fatty foods, oils, or strong-smelling foods like garlic, curry, and onions, can seep through your pores and cause body odor. (Always see a doctor or dietician before making drastic dietary changes.)
6. If you have excessive sweating (called hyperhidrosis), talk to your doctor. There are many treatment options for those with more severe sweating who desire more permanent treatments. Also, certain medical problems can lead to excessive sweating. Your doctor can make a diagnosis and prescribe treatment.
7. Shaving your underarm regularly will help prevent the accumulation of bacteria and can reduce sweat and odor.

In some societies, body odor is accepted. But most countries today frown on body odor. In fact, some religions have strict guidelines about bathing practices and personal hygiene.

The best way to fight body odor is through prevention. For most teens, proper hygiene -- like washing well and applying an underarm antiperspirant or deodorant -- should be enough.

Researchers obtained the body odors in the present study by paying a group of male and female heterosexual and homosexual "odor donors" to avoid all fragrances, soaps, and shampoos for 9 days. During this time they could not shave their armpits or eat spicy food. Following this preparation they wore cotton gauze pads under their arms for three days. These pads were later cut up and places in plastic squeeze bottles for use in the study.

A different group of subjects, the "odor evaluators" were paid to rate the different odor combinations without knowing which group the odors came from. Significant differences emerged:

• Heterosexual males found the odors of heterosexual females to be the least unpleasant, and the odors of gay males to be the most unpleasant.
• Gay males found the odors of heterosexual females to be least unpleasant, but the odors of gay males followed close behind. The odors of lesbians and heterosexual males were judged most unpleasant (but the overall differences were smaller for gay males than for other "odor evaluators").
• Heterosexual females found the odors of gay males and lesbians to be more unpleasant than the odors of other heterosexual females and heterosexual males.
• Lesbians preferred the odors of heterosexual females and especially disliked the odors of gay males.

Some of these results make more sense than others. Taken together, they do demonstrate that both gender and sexual orientation affect our preference for human body odors. The study was conducted in Philadelphia, in the United States; and most participants found all of the odors to be somewhat unpleasant. As we get closer to the people in our lives we do inevitably smell them. What we smell may make more of a difference than we think.