Body odor

Body odor or body odour, sometimes colloquially abbreviated as B.O., is the smell of bacteria growing on the body. The bacteria multiply rapidly in the presence of sweat, but sweat itself is almost completely odorless to humans.

Body odor
Classification and external resources
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DiseasesDB	28886
eMedicine	derm/597

This condition can be known medically as bromhidrosis, apocrine bromhidrosis, bromidrosis, osmidrosis, ozochrotia, fetid sweat, body smell or malodorous sweating.

Specificity

Body odor can smell pleasant and specific to the individual and can be used to identify people, though this is more often done by dogs and other animals than by humans. An individual's body odor is also influenced by diet, lifestyle, gender, genetics, health and medication.

Propionic acid (propanoic acid) is present in many sweat samples. This acid is a breakdown product of some amino acids by propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. Because propionic acid is chemically similar to acetic acid with similar characteristics including odor, body odors may be identified as having a vinegar-like smell by certain people. Isovaleric acid (3-methyl butanoic acid) is the other source of body odor as a result of actions of the bacteria Staphylococcus epidermidis, which is also present in several strong cheese types.

Genetics

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.

One study suggests that body odor is genetically determined by a gene that also codes the type of earwax one has. East Asians (those of Chinese, Japanese, Korean, and Vietnamese descent) have the type of sweat glands that even after hitting puberty still don't produce the chemicals found in the perspiration of other ancestral groups. 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.

Alterations

Body odor may be reduced or prevented or even aggravated by using deodorants, antiperspirants, disinfectants (e.g., triclosan), special soaps or foams with antiseptic plant extracts such as ribwort and liquorice, chlorophyllin ointments and sprays topically, and chlorophyllin supplements internally. Although body odor is commonly associated with hygiene practices, its presentation can be affected by changes in diet as well as the other factors discussed above.

Causes

Body odor is caused by the actions of skin flora, including members of Corynebacterium, which manufacture enzymes called lipases that break down the lipids in sweat to create smaller molecules like butyric acid. These smaller molecules smell, and give body odor its characteristic aroma.

See also

• Butyric acid
• Drug resistance
• Foot odor
• Halitosis (bad breath)           
• Human flora

• Olfactophilia
• Pheromone
• Sweat gland
• Trimethylaminuria
• Underarm liners
• Body odor and subconscious human sexual attraction

References

Notes

External links

• Flores G (2004). "Immunity, smell linked". The Scientist. 5 (1).
• Male sweat boosts women's hormone levels -- from UC Berkeley, February 2007
• "Odors and metabolic disease" from Miami Children's Brain Institute
• Causes of body odor

• What is body odour? - Medical article, December 2009.

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