Editing Body odor

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{{short description|Odor produced by a living animal}}
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{{Use American English|date=March 2021}}
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'''Body odor''' or '''body odour''' ('''BO''') is present in all animals and its intensity can be influenced by many factors (behavioral patterns, survival strategies). Body odor has a strong genetic basis, but can also be strongly influenced by various factors, such as sex, diet, health, and medication.<ref name="lund-4">{{cite journal |last1=Lundström |first1=Johan N. |last2=Olsson |first2=Mats J. |title=Functional Neuronal Processing of Human Body Odors |journal=Vitamins & Hormones |date=2010 |volume=83 |pages=1–23 |doi=10.1016/S0083-6729(10)83001-8 |pmid=20831940 |pmc=3593650 |isbn=978-0-12-381516-3 }}</ref> The body odor of human males plays an important [[Body odour and sexual attraction|role in human sexual attraction]], as a powerful indicator of [[Major histocompatibility complex|MHC]]/[[Human leukocyte antigen|HLA]] heterozygosity.<ref name="Grammer_2005"/><ref name="lund-4" /> Significant evidence suggests that women are attracted to men whose body odor is different from theirs, indicating that they have immune genes that are different from their own, which may produce healthier offspring.<ref>{{cite magazine |last1=Everts |first1=Sarah |title=What Your Body Odor Says About You |url=https://time.com/6082321/your-body-odor-says-about-you/ |magazine=Time |language=en |date=21 July 2021 |quote= "In one study about smell and romance, straight women preferred the body odor of straight men whose immune systems were different enough that any offspring would have healthy immune systems. For most of human history, infectious disease has been our greatest threat. In modern times we may seek life-partners that satisfy a multitude of needs, but more fundamentally, if you could produce babies with immune systems able to fight a potpourri of pathogens, then your progeny—and your genes—stand a better chance at survival."}}</ref>

==Causes==
{{See also|Biochemistry of body odor}}
In humans, the formation of body odors is caused by factors such as diet, sex, health, and medication, but the major contribution comes from [[bacteria]]l activity on [[skin gland]] [[secretion]]s.<ref name="lund-4" /> Humans have three types of sweat glands: [[eccrine sweat glands]], [[apocrine sweat gland]]s and [[sebaceous gland]]s. Eccrine sweat glands are present from birth, while the latter two become activated during puberty. Among the different types of human skin glands, body odor is primarily the result of the apocrine sweat glands, which secrete the majority of chemical compounds that the [[skin flora]] metabolize into odorant substances.<ref name="lund-4"/> This happens mostly in the axillary (armpit) region, although the gland can also be found in the [[areola]], anogenital region, and around the [[navel]].<ref>{{cite book| vauthors = Turkington C, Dover JS | title=The encyclopedia of skin and skin disorders| url=https://archive.org/details/encyclopediaskin00turk| url-access=limited| year=2007| publisher=Facts on File|location=New York| isbn=978-0-8160-6403-8| pages=[https://archive.org/details/encyclopediaskin00turk/page/n383 363]| edition=3rd}}</ref> In humans, the [[armpit]] regions seem more important than the genital region for body odor, which may be related to human [[bipedalism]]. The genital and armpit regions also contain springy hairs which help diffuse body odors.<ref name=Oxford2007/>

The main components of human axillary odor are [[Saturated fat|unsaturated]] or [[Hydroxylation|hydroxylated]] branched [[fatty acid]]s with E-3-methylhex-2-enoic acid (E-3M2H) and 3-hydroxy-3-methylhexanoic acid (HMHA), sulfanylalkanols and particularly 3-methyl-3-sulfanylhexan-1-ol (3M3SH), and the odoriferous steroids [[androstenone]] (5α-androst-16-en-3-one) and [[androstenol]] (5α-androst-16-en-3α-ol).<ref name=martessbio/> E-3M2H is bound and carried by two apocrine secretion odor-binding proteins, ASOB1 and ASOB2, to the skin surface.<ref>{{cite journal | vauthors = Zeng C, Spielman AI, Vowels BR, Leyden JJ, Biemann K, Preti G | title = A human axillary odorant is carried by apolipoprotein D | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 93 | issue = 13 | pages = 6626–6630 | date = June 1996 | pmid = 8692868 | pmc = 39076 | doi = 10.1073/pnas.93.13.6626 | doi-access = free | bibcode = 1996PNAS...93.6626Z }}</ref>

Body odor is influenced by the actions of the [[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]]. Greater bacteria populations of ''[[Corynebacterium jeikeium]]'' are found more in the armpits of men, whereas greater population numbers of ''[[Staphylococcus haemolyticus]]'' are found in the armpits of women. This causes male armpits to give off a rancid/cheese-like smell, whereas female armpits give off a more fruity/onion-like smell.<ref>{{cite book | vauthors = Kort R | title = De microbemens: Het belang van het onzichtbare leven. | trans-title = The microbes: The importance of the invisible life. | language = Dutch | location = Amsterdam | publisher = Athenaeum, Polak & Van Gennep | date = September 2017 | isbn = 978-90-253-0692-2 }}</ref> ''[[Staphylococcus hominis]]'' is also known for producing [[thioalcohol]] compounds that contribute to odors.<ref>{{cite press release |title=Bacterial genetic pathway involved in body odor production discovered |url=https://www.sciencedaily.com/releases/2015/03/150330213947.htm |publisher=Society for General Microbiology |date=30 March 2015 }}</ref> These smaller molecules smell, and give body odor its characteristic aroma.<ref>{{cite book | vauthors = Buckman R |title=Human Wildlife: The Life That Lives On Us. |date=2003 |publisher=The Johns Hopkins University Press |location=Baltimore, Md. |isbn=978-0-8018-7407-9 | pages = 93–94 }}</ref> [[Propionic acid]] (propanoic acid) is present in many sweat samples. This acid is a breakdown product of some [[amino acid]]s 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 pungent, cheesy and vinegar-like smell although certain people might find it pleasant at lower concentrations.<ref>{{cite journal | url=https://pubmed.ncbi.nlm.nih.gov/10637054/ | pmid=10637054 | date=2000 | last1=Charles | first1=M. | last2=Martin | first2=B. | last3=Ginies | first3=C. | last4=Etievant | first4=P. | last5=Coste | first5=G. | last6=Guichard | first6=E. | title=Potent aroma compounds of two red wine vinegars | journal=Journal of Agricultural and Food Chemistry | volume=48 | issue=1 | pages=70–77 | doi=10.1021/jf9905424 | bibcode=2000JAFC...48...70C }}</ref> [[Isovaleric acid]] (3-methyl butanoic acid) is the other source of body odor as a result of actions of the bacteria ''[[Staphylococcus epidermidis]]'',<ref>{{cite journal | vauthors = Ara K, Hama M, Akiba S, Koike K, Okisaka K, Hagura T, Kamiya T, Tomita F | title = Foot odor due to microbial metabolism and its control | journal = Canadian Journal of Microbiology | volume = 52 | issue = 4 | pages = 357–364 | date = April 2006 | pmid = 16699586 | doi = 10.1139/w05-130 | citeseerx = 10.1.1.1013.4047 }}</ref> which is also present in several types of strong cheese.

Factors such as food, drink, gut microbiome,<ref>{{Cite journal |url=https://derma.jmir.org/2020/1/e10508 |doi=10.2196/10508 |title=Cutaneous Bacteria in the Gut Microbiome as Biomarkers of Systemic Malodor and People Are Allergic to Me (PATM) Conditions: Insights from a Virtually Conducted Clinical Trial |date=2020 |last1=Gabashvili |first1=Irene S. |journal=JMIR Dermatology |volume=3 |pages=e10508 |s2cid=226280399 |doi-access=free }}</ref> and [[genetics]] can affect body odor.<ref name=Oxford2007/>

== Function ==
{{See also|Pheromone}}

===Animals===
In many animals, body odor plays an important survival function. Strong body odor can be a [[warning signal]] for predators to stay away (such as [[North American porcupine#Stench|porcupine stink]]), or it can also be a signal that the prey animal is [[unpalatable]].<ref>{{cite book | vauthors = Ruxton GD, Allen WL, Sherratt TN, Speed MP |title=Avoiding Attack: The Evolutionary Ecology of Crypsis, Aposematism, and Mimicry |year=2018 |publisher=Oxford University Press |isbn=978-0-19-186849-8 }}{{page needed|date=September 2020}}</ref> For example, some animal species that feign death to survive (like [[opossum]]s), in this state produce a strong body odor to deceive a predator that the prey animal has been dead for a long time and is already in the advanced stage of decomposing. Some animals with strong body odor are rarely attacked by most predators, although they can still be killed and eaten by birds of prey, which are tolerant of carrion odors.{{citation needed|date=March 2022}}

Body odor is an important feature of animal physiology. It plays a different role in different animal species. For example, in some predator species that hunt by stalking (such as big and small [[cat]]s), the absence of body odor is important, and they spend plenty of time and energy to keep their body free of odor. For other predators, such as those that hunt by visually locating prey and running for long distances after it (such as [[dog]]s and [[Gray wolf|wolves]]), the absence of body odor is not critical. In most animals, body odor intensifies in moments of stress and danger.<ref>{{cite journal | vauthors = Takahashi LK | title = Olfactory systems and neural circuits that modulate predator odor fear | journal = Frontiers in Behavioral Neuroscience | volume = 8 | pages = 72 | date = 11 March 2014 | pmid = 24653685 | pmc = 3949219 | doi = 10.3389/fnbeh.2014.00072 | doi-access = free }}</ref>

====Humans====
In humans, body odor serves as a means of chemosensory signal communication between members of the species. These signals are called [[pheromone]]s and they can be transmitted through a variety of mediums. The most common way that human pheromones are transmitted is through bodily fluids. Human pheromones are contained in sweat, semen, vaginal secretions, breast milk, and urine.<ref name="lund-4" /> The signals carried in these fluids serve a range of functions from reproductive signaling to infant socialization.<ref name="Damon_2021">{{cite journal | vauthors = Damon F, Mezrai N, Magnier L, Leleu A, Durand K, Schaal B | title = Olfaction in the Multisensory Processing of Faces: A Narrative Review of the Influence of Human Body Odors | journal = Frontiers in Psychology | volume = 12 | pages = 750944 | date = 2021-10-05 | pmid = 34675855 | pmc = 8523678 | doi = 10.3389/fpsyg.2021.750944 | doi-access = free }}</ref> Each person produces a unique spread of pheromones that can be identified by others.<ref name="Grammer_2005">{{cite journal | vauthors = Grammer K, Fink B, Neave N | title = Human pheromones and sexual attraction | journal = European Journal of Obstetrics, Gynecology, and Reproductive Biology | volume = 118 | issue = 2 | pages = 135–142 | date = February 2005 | pmid = 15653193 | doi = 10.1016/j.ejogrb.2004.08.010 }}</ref> This differentiation allows the formation of sexual attraction and kinship ties to occur.<ref name="Grammer_2005" /><ref name="Porter_1985">{{cite journal | vauthors = Porter RH, Cernoch JM, Balogh RD | title = Odor signatures and kin recognition | journal = Physiology & Behavior | volume = 34 | issue = 3 | pages = 445–448 | date = March 1985 | pmid = 4011726 | doi = 10.1016/0031-9384(85)90210-0 | s2cid = 42316168 }}</ref>

[[Sebaceous]] and [[apocrine gland]]s become active at [[puberty]]. This, as well as many apocrine glands being close to the sex organs, points to a role related to mating.<ref name="Oxford2007" /> Sebaceous glands line the human skin while apocrine glands are located around body hairs.<ref name="lund-4" /> Compared to other primates, humans have extensive axillary hair and have many odor producing sources, in particular many apocrine glands.<ref name="AEP" /> In humans, the apocrine glands have the ability to secrete [[pheromone]]s. These steroid compounds are produced within the peroxisomes of the apocrine glands by enzymes such as mevalonate kinases.<ref>{{cite journal | vauthors = Rothardt G, Beier K | title = Peroxisomes in the apocrine sweat glands of the human axilla and their putative role in pheromone production | journal = Cellular and Molecular Life Sciences | volume = 58 | issue = 9 | pages = 1344–1349 | date = August 2001 | pmid = 11577991 | doi = 10.1007/PL00000946 | s2cid = 28790000 | pmc = 11337405 }}</ref>

==== Sexual selection ====
Pheromones are a factor seen in the mating selection and reproduction in humans. In women, the sense of olfaction is strongest around the time of [[ovulation]], significantly stronger than during other phases of the [[menstrual cycle]] and also stronger than the sense in males.<ref>{{harvnb|Lundström|Olsson|2010|ps=:"In addition, the impact that biological factors have on our percept of body odors has recently been indirectly demonstrated by several experiments. Our percept of body odors is dependent on the sexual orientations of both the donor and the perceiver (Martins et al., 2005), and heterosexual women's percept of men's body odor varies over their menstrual cycle (Roberts et al., 2004)."}}</ref><ref>{{cite journal | vauthors = Navarrete-Palacios E, Hudson R, Reyes-Guerrero G, Guevara-Guzmán R | title = Lower olfactory threshold during the ovulatory phase of the menstrual cycle | journal = Biological Psychology | volume = 63 | issue = 3 | pages = 269–279 | date = July 2003 | pmid = 12853171 | doi = 10.1016/s0301-0511(03)00076-0 | s2cid = 46065468 | doi-access = free }}</ref> Pheromones can be used to deliver information about the [[major histocompatibility complex]] (MHC).<ref name="Grammer_2005"/>   The MHC in humans is referred to as the [[Human leukocyte antigen|Human Leukocyte Antigen]] (HLA).<ref name="Kromer_2016">{{cite journal | vauthors = Kromer J, Hummel T, Pietrowski D, Giani AS, Sauter J, Ehninger G, Schmidt AH, Croy I | title = Influence of HLA on human partnership and sexual satisfaction | journal = Scientific Reports | volume = 6 | pages = 32550 | date = August 2016 | pmid = 27578547 | pmc = 5006172 | doi = 10.1038/srep32550 | bibcode = 2016NatSR...632550K }}</ref> Each type has a unique scent profile that can be utilized during the mating selection process. When selecting mates, women tend to be attracted to those that have different HLA-types than their own.<ref name="Grammer_2005" /><ref name="Kromer_2016" />  This is thought to increase the strength of the family unit and increase the chances of survival for potential offspring.<ref name="Grammer_2005" />

Studies have suggested that people might be using odor cues associated with the immune system to select mates. Using a brain-imaging technique, Swedish researchers have shown that [[homosexuality|homosexual]] and [[heterosexuality|heterosexual]] males' brains respond in different ways to two odors that may be involved in sexual arousal, and that homosexual men respond in the same way as heterosexual women, though it could not be determined whether this was cause or effect. When the study was expanded to include lesbian women, the results were consistent with previous findings – meaning that lesbian women were not as responsive to male-identified odors, while responding to female odors in a similar way as heterosexual males.<ref>{{cite journal |vauthors=Berglund H, Lindström P, Savic I |date=May 2006 |title=Brain response to putative pheromones in lesbian women |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=103 |issue=21 |pages=8269–8274 |bibcode=2006PNAS..103.8269B |doi=10.1073/pnas.0600331103 |pmc=1570103 |pmid=16705035 |doi-access=free}}</ref> According to the researchers, this research suggests a possible role for human pheromones in the biological basis of [[sexual orientation]].<ref>{{cite news |date=9 May 2005 |title=Gay Men Are Found to Have Different Scent of Attraction |work=The New York Times |url=https://www.nytimes.com/2005/05/09/science/09cnd-smell.html |vauthors=Wade N}}</ref>

==== Kinship communication ====
Humans can olfactorily detect blood-related kin.<ref name="Porter_1985"/> Mothers can identify by body odor their biological children, but not their stepchildren. Preadolescent children can olfactorily detect their full siblings, but not half-siblings or step-siblings, and this might explain [[inbreeding avoidance|incest avoidance]] and the [[Westermarck effect]].<ref>{{cite journal | vauthors = Weisfeld GE, Czilli T, Phillips KA, Gall JA, Lichtman CM | title = Possible olfaction-based mechanisms in human kin recognition and inbreeding avoidance | journal = Journal of Experimental Child Psychology | volume = 85 | issue = 3 | pages = 279–295 | date = July 2003 | pmid = 12810039 | doi = 10.1016/s0022-0965(03)00061-4 }}</ref> Babies can recognize their mothers by smell while mothers, fathers, and other relatives can identify a baby by smell.<ref name="Oxford2007" /> This connection between genetically similar family members is due to the habituation of familial pheromones. In the case of babies and mothers, this chemosensory information is primarily contained within breastmilk and the mother's sweat. When compared to that of strangers, babies are observed to have stronger neural connections with their mothers.<ref name="Endevelt-Shapira_2021">{{cite journal | vauthors = Endevelt-Shapira Y, Djalovski A, Dumas G, Feldman R | title = Maternal chemosignals enhance infant-adult brain-to-brain synchrony | journal = Science Advances | volume = 7 | issue = 50 | pages = eabg6867 | date = December 2021 | pmid = 34890230 | pmc = 8664266 | doi = 10.1126/sciadv.abg6867 | bibcode = 2021SciA....7.6867E }}</ref> This strengthened neurological connection allows for the biological development and socialization of the infant by their mother. Using these connections, the mother transmits olfactory signals to the infant which are then perceived and integrated.<ref name="Endevelt-Shapira_2021" />

In terms of biological functioning, olfactory signaling allows for functional [[breastfeeding]] to occur. In cases of effective latching, breastfed infants are able to locate their mother's nipples for feeding using the sensory information enclosed in their mother's body odor.<ref name="Varendi_1994">{{cite journal | vauthors = Varendi H, Porter RH, Winberg J | title = Does the newborn baby find the nipple by smell? | language = English | journal = Lancet | volume = 344 | issue = 8928 | pages = 989–990 | date = October 1994 | pmid = 7934434 | doi = 10.1016/S0140-6736(94)91645-4 | s2cid = 35029502 }}</ref> While no specific human breast pheromones have been identified, studies compare the communication to that of the rabbit mammary pheromone 2MB2.<ref>{{Citation | vauthors = Schaal B |title=Pheromones for Newborns |date=2014 |url=http://www.ncbi.nlm.nih.gov/books/NBK200997/ |work=Neurobiology of Chemical Communication | veditors = Mucignat-Caretta C |series=Frontiers in Neuroscience |place=Boca Raton (FL) |publisher=CRC Press/Taylor & Francis |isbn=978-1-4665-5341-5 |pmid=24830031 |access-date=2022-11-27}}</ref><ref>{{Cite web |title=Pheromone From Mother's Milk May Rapidly Promote Learning In Newborn Mammals |url=https://www.sciencedaily.com/releases/2006/10/061010022813.htm |access-date=2022-11-27 |website=ScienceDaily |language=en}}</ref> The perception and integration of these signals is an evolutionary response that allows newborns to locate their source of nutrition. Signaling contains a level of precision that allows babies to differentiate their mother's breasts from that of other women. Once the baby recognizes the familiar olfactory signal, the behavioral response of latching follows. Over time the infant becomes habituated to their mother's breast pheromones which increases latch efficiency.<ref name="Varendi_1994" />

Beyond a biological function, a mother's body odor plays a role in developing a baby's social capabilities. The ability of an infant to evaluate the properties of human faces stems from the olfactory cues given from their mother.<ref name="Damon_2021"/> Frequent exposure to the [[pheromone]]s exuded by their mother allows the connection between vision and smell to form in infants.<ref name="Endevelt-Shapira_2021" /> This type of connection is only found between mothers and babies and over time it socializes the ability to recognize the features that distinguish human faces from inanimate objects.<ref name="Damon_2021" />

==== Environmental threats ====
The connection between olfactory and visual cues has also been observed outside of familial relationships. Evolutionarily, body odor has been used to communicate messages about potentially dangerous stimuli in the environment.<ref name="lund-4" />  Body odor produced during particularly stressful situations can produce a cascade of reactions in the brain. Once the olfactory system is activated by a threatening stimuli, heightened activity in the [[amygdala]] and [[Occipital lobe|occipital cortex]] is triggered.<ref>{{cite journal | vauthors = Mujica-Parodi LR, Strey HH, Frederick B, Savoy R, Cox D, Botanov Y, Tolkunov D, Rubin D, Weber J | title = Chemosensory cues to conspecific emotional stress activate amygdala in humans | journal = PLOS ONE | volume = 4 | issue = 7 | pages = e6415 | date = July 2009 | pmid = 19641623 | pmc = 2713432 | doi = 10.1371/journal.pone.0006415 | bibcode = 2009PLoSO...4.6415M | doi-access = free }}</ref><ref name="lund-4" /> This chain reaction serves to help assess the nature of the threat and increase chance of survival.

Humans have few olfactory receptor cells compared to dogs and few functional olfactory receptor genes compared to rats. This is in part due to a reduction of the size of the snout in order to achieve [[depth perception]] as well as other changes related to bipedalism. However, it has been argued that humans may have larger brain areas associated with olfactory perception compared to other species.<ref name=AEP>{{cite book |doi= 10.1093/acprof:oso/9780199586073.003.0020 |chapter=Evolutionary psychology and perfume design |title=Applied Evolutionary Psychology |year=2011 | vauthors = Roberts SC, Havlicek J |pages=330–348 |isbn=978-0-19-958607-3 }}</ref>

==Genes affecting body odor==
{{See also|Major histocompatibility complex and sexual selection|Body odor and subconscious human sexual attraction|ABCC11}}
[[File:World_map_ABCC11_A_Allele.svg|thumb|250px|World map of the distribution of the A allele of the single nucleotide polymorphism rs17822931 in the [[ABCC11|ABCC11 gene]]. The proportion of A alleles in each population is represented by the white area in each circle.]]

=== MHC ===
Body odor is influenced by [[major histocompatibility complex]] (MHC) molecules. These are genetically determined and play an important role in [[immunity (medical)|immunity]] of the organism. The [[vomeronasal organ]] contains cells sensitive to MHC molecules in a genotype-specific way.{{citation needed|date=March 2022}}

Experiments on animals and volunteers have shown that potential sexual partners tend to be perceived more attractive if their MHC composition is substantially different. Married couples are more different regarding MHC genes than would be expected by chance. This behavior pattern promotes variability of the immune system of individuals in the population, thus making the population more robust against new diseases. Another reason may be to prevent [[inbreeding]].<ref name=Oxford2007>{{cite book | vauthors = Wedekind C |chapter=Body Odours and Body Odour Preferences in Humans |doi=10.1093/oxfordhb/9780198568308.013.0022 |year=2007 |title=Oxford Handbook of Evolutionary Psychology |pages=315–320 |isbn=978-0-19-174365-8 }}</ref>

=== ABCC11 ===
The [[ABCC11]] gene determines axillary body odor and the type of [[earwax]].<ref name=martessbio/><ref name=yosh06>{{cite journal | vauthors = Yoshiura K, Kinoshita A, Ishida T, Ninokata A, Ishikawa T, Kaname T, Bannai M, Tokunaga K, Sonoda S, Komaki R, Ihara M, Saenko VA, Alipov GK, Sekine I, Komatsu K, Takahashi H, Nakashima M, Sosonkina N, Mapendano CK, Ghadami M, Nomura M, Liang DS, Miwa N, Kim DK, Garidkhuu A, Natsume N, Ohta T, Tomita H, Kaneko A, Kikuchi M, Russomando G, Hirayama K, Ishibashi M, Takahashi A, Saitou N, Murray JC, Saito S, Nakamura Y, Niikawa N | title = A SNP in the ABCC11 gene is the determinant of human earwax type | journal = Nature Genetics | volume = 38 | issue = 3 | pages = 324–330 | date = March 2006 | pmid = 16444273 | doi = 10.1038/ng1733 | s2cid = 3201966 }}</ref><ref name=kanlay>{{cite journal | vauthors = Kanlayavattanakul M, Lourith N | title = Body malodours and their topical treatment agents | journal = International Journal of Cosmetic Science | volume = 33 | issue = 4 | pages = 298–311 | date = August 2011 | pmid = 21401651 | doi = 10.1111/j.1468-2494.2011.00649.x | doi-access = free }}</ref><ref name=nakmotstrasso>{{cite journal | vauthors = Nakano M, Miwa N, Hirano A, Yoshiura K, Niikawa N | title = A strong association of axillary osmidrosis with the wet earwax type determined by genotyping of the ABCC11 gene | journal = BMC Genetics | volume = 10 | issue = 1 | pages = 42 | date = August 2009 | pmid = 19650936 | pmc = 2731057 | doi = 10.1186/1471-2156-10-42 | doi-access = free }}</ref> The loss of a functional ABCC11 gene is caused by a 538G>A [[single-nucleotide polymorphism]], resulting in a loss of body odor in people who are specifically homozygous for it.<ref name=nakmotstrasso/><ref>{{cite journal | vauthors = Preti G, Leyden JJ | title = Genetic influences on human body odor: from genes to the axillae | journal = The Journal of Investigative Dermatology | volume = 130 | issue = 2 | pages = 344–346 | date = February 2010 | pmid = 20081888 | doi = 10.1038/jid.2009.396 | doi-access = free }}</ref> Firstly, it affects [[apocrine sweat gland]]s by reducing secretion of odorous molecules and its precursors.<ref name=martessbio>{{cite journal | vauthors = Martin A, Saathoff M, Kuhn F, Max H, Terstegen L, Natsch A | title = A functional ABCC11 allele is essential in the biochemical formation of human axillary odor | journal = The Journal of Investigative Dermatology | volume = 130 | issue = 2 | pages = 529–540 | date = February 2010 | pmid = 19710689 | doi = 10.1038/jid.2009.254 | doi-access = free }}</ref> The lack of ABCC11 function results in a decrease of the odorant compounds 3M2H, HMHA, and 3M3SH via a strongly reduced secretion of the precursor amino-acid conjugates 3M2H–Gln, HMHA–Gln, and Cys–Gly–(S) 3M3SH; and a decrease of the odoriferous steroids androstenone and androstenol, possibly due to the reduced secretion of [[dehydroepiandrosterone sulfate]] (DHEAS) and [[dehydroepiandrosterone]] (DHEA), possibly bacterial substrates for odoriferous steroids; research has found no difference, however, in testosterone secretion in apocrine sweat between ABCC11 mutants and non-mutants.<ref name=martessbio/> Secondly, it is also associated with a strongly reduced/atrophic size of apocrine sweat glands and a decreased protein (such as ASOB2) concentration in axillary sweat.<ref name=martessbio/>

The non-functional ABCC11 allele is predominant among [[East Asians]] (80–95%), but very low among European and African populations (0–3%).<ref name=martessbio/> Most of the world's population has the gene that codes for the wet-type earwax and average body odor; however, East Asians are more likely to inherit the allele associated with the dry-type earwax and a reduction in body odor.<ref name=martessbio/><ref name=yosh06/><ref name=nakmotstrasso/> The reduction in body odor may be due to adaptation to colder climates by their ancient Northeast Asian ancestors.<ref name=yosh06/>

However, research has observed that this allele is not solely responsible for ethnic differences in scent. A 2016 study analyzed differences across ethnicities in volatile organic compounds (VOCs), across racial groups and found that while they largely did not differ significantly qualitatively, they did differ quantitatively. Of the observed differences, they were found to vary with ethnic origin, but not entirely with ABCC11 genotype.<ref name="auto">{{cite journal | vauthors = Prokop-Prigge KA, Greene K, Varallo L, Wysocki CJ, Preti G | title = The Effect of Ethnicity on Human Axillary Odorant Production | journal = Journal of Chemical Ecology | volume = 42 | issue = 1 | pages = 33–39 | date = January 2016 | pmid = 26634572 | pmc = 4724538 | doi = 10.1007/s10886-015-0657-8 | bibcode = 2016JCEco..42...33P }}</ref>

One large study failed to find any significant differences across ethnicity in residual compounds on the skin, including those located in sweat.<ref>{{cite journal | vauthors = Shetage SS, Traynor MJ, Brown MB, Raji M, Graham-Kalio D, Chilcott RP | title = Effect of ethnicity, gender and age on the amount and composition of residual skin surface components derived from sebum, sweat and epidermal lipids | journal = Skin Research and Technology | volume = 20 | issue = 1 | pages = 97–107 | date = February 2014 | pmid = 23865719 | pmc = 4285158 | doi = 10.1111/srt.12091 }}</ref> If there were observed ethnic variants in skin odor, one would find sources to be much more likely in diet, hygiene, microbiome, and other environmental factors.<ref>{{cite journal | vauthors = Tullett W |title=Grease and Sweat: Race and Smell in Eighteenth-Century English Culture |journal=Cultural and Social History |date=2 July 2016 |volume=13 |issue=3 |pages=307–322 |doi=10.1080/14780038.2016.1202008 |s2cid=147837009 |doi-access=free }}</ref><ref name="auto"/><ref>{{cite journal | vauthors = Li M, Budding AE, van der Lugt-Degen M, Du-Thumm L, Vandeven M, Fan A | title = The influence of age, gender and race/ethnicity on the composition of the human axillary microbiome | journal = International Journal of Cosmetic Science | volume = 41 | issue = 4 | pages = 371–377 | date = August 2019 | pmid = 31190339 | doi = 10.1111/ics.12549 | s2cid = 189816630 }}</ref>

Research has indicated a strong association between people with axillary osmidrosis and the ABCC11-genotypes GG or GA at the SNP site (rs17822931) in comparison to the genotype AA.<ref name=nakmotstrasso/>

'''Age-Related Differences'''

As seen in non-human animals such as mice, black-tailed deer, rabbits, otters, and owl monkeys, body odor contains age-related signals that these animals can detect and process. Similarly, humans have been seen to distinguish age-related information from body odor, particularly relating to odors of those of old age. In a study determining if there is a difference between the body odor of individuals of various ages, three groups were studied: those aged 20-30, aged 45-55, and aged 75-95, corresponding to young age, middle-aged, and old age, respectively. This study determined that individuals could distinguish between odors of various ages and group odors of old age, suggesting that there are certain chemical differences in age resulting in “age-dependent odor characteristics”.<ref>{{cite journal |last1=Mitro |first1=Susanna |last2=Gordon |first2=Amy R. |last3=Olsson |first3=Mats J. |last4=Lundström |first4=Johan N. |title=The Smell of Age: Perception and Discrimination of Body Odors of Different Ages |journal=PLOS ONE |date=May 30, 2012 |volume=7 |issue=5 |pages=e38110 |doi=10.1371/journal.pone.0038110 |doi-access=free |pmid=22666457 |pmc=3364187 |bibcode=2012PLoSO...738110M }}</ref>

Another study evaluated the components of body odor in participants aged 26 through 75 using headspace gas chromatography and mass spectroscopy. This study demonstrated that in individuals 40 years or older, 2-Nonenal, an unsaturated aldehyde producing a greasy and grassy odor, was detected in increasing concentrations of those individuals. The detection of increasing amounts of 2-Nonenal in individuals 40 years or older suggested that 2-Nonenal contributes to the deteriorating body odor seen with aging.<ref>{{cite journal |last1=Haze |first1=Shinichiro |last2=Gozu |first2=Yoko |last3=Nakamura |first3=Shoji |last4=Kohno |first4=Yoshiyuki |last5=Sawano |first5=Kiyohito |last6=Ohta |first6=Hideaki |last7=Yamazaki |first7=Kazuo |title=2-Nonenal Newly Found in Human Body Odor Tends to Increase with Aging |journal=Journal of Investigative Dermatology |date=December 8, 2015 |volume=116 |issue=4 |pages=520–524|doi=10.1046/j.0022-202x.2001.01287.x |doi-access=free |pmid=11286617 }}</ref>

'''Body Odor and Disease'''

In mammals, body odor can also be used as a symptom of disease. One's body odor is completely unique to themselves, similar to a fingerprint, and can change due to sexual life, genetics, age and diet. Body odor, however, can be used as an indication for disease. For example, typically, human urine contains 95% water,<ref>{{cite journal |last1=Sarigul |first1=Nesilhan |title=A New Artificial Urine Protocol to Better Imitate Human Urine |journal=Scientific Reports |date=2019 |volume=9 |issue=1 |page=20159 |doi=10.1038/s41598-019-56693-4 |pmid=31882896 |pmc=6934465 |bibcode=2019NatSR...920159S }}</ref> however, for a person with an abnormal amount of blood sugar, their urine becomes more concentrated with glucose.<ref>{{cite book |last1=Siyang |first1=Satetha |title=The 5th 2012 Biomedical Engineering International Conference |chapter=Diabetes diagnosis by direct measurement from urine odor using electronic nose |date=2012 |pages=1–4 | via=IEEE conference publication |chapter-url=https://ieeexplore.ieee.org/document/6465441 |publisher=IEEE|doi=10.1109/BMEiCon.2012.6465441 |isbn=978-1-4673-4892-8 }}</ref> Therefore, if a person's body odor or urine smells unusually fruity or sweet, that can be a sign of diabetes. Additionally, an ammonia smell that occurs in one's body, urine, or breath could also be an indicator of kidney disease. Typically, the liver converts ammonia to urea because ammonia has a high level of toxicity. The kidneys are responsible for removing waste, such as urea, out from the body. However, if the kidneys are not functioning properly, this urea is kept as ammonia, causing the urine and even one's breath to smell like ammonia.<ref>{{cite journal |last1=Chan |first1=Ming-Jen |title=Breath Ammonia Is a Useful Biomarker Predicting Kidney Function in Chronic Kidney Disease Patients |date=2020 |volume=8 |issue=11 |page=468 |journal=Biomedicines|doi=10.3390/biomedicines8110468 |doi-access=free |pmid=33142890 |pmc=7692127 }}</ref> In conclusion, body odor could be used as a helpful indicator of disease, especially when it suddenly deviates from normal.


{| class="wikitable"
|+Frequencies of ABCC11 allele c.538 (One nonsynonymous SNP 538G > A)<ref name="pmid23316210">{{cite journal | vauthors = Ishikawa T, Toyoda Y, Yoshiura K, Niikawa N | title = Pharmacogenetics of human ABC transporter ABCC11: new insights into apocrine gland growth and metabolite secretion | journal = Frontiers in Genetics | volume = 3 | issue = | pages = 306 | date = 2012 | pmid = 23316210 | pmc = 3539816 | doi = 10.3389/fgene.2012.00306 | doi-access = free }}</ref><ref>{{cite journal |last1=Miura |first1=Kiyonori |last2=Yoshiura |first2=Koh-ichiro |last3=Miura |first3=Shoko |last4=Shimada |first4=Takako |last5=Yamasaki |first5=Kentaro |last6=Yoshida |first6=Atsushi |last7=Nakayama |first7=Daisuke |last8=Shibata |first8=Yoshisada |last9=Niikawa |first9=Norio |last10=Masuzaki |first10=Hideaki |title=A strong association between human earwax-type and apocrine colostrum secretion from the mammary gland |journal=Human Genetics |date=June 2007 |volume=121 |issue=5 |pages=631–633 |doi=10.1007/s00439-007-0356-9 |pmid=17394018 |s2cid=575882 |url=https://pubmed.ncbi.nlm.nih.gov/17394018/ |issn=0340-6717}}</ref>
! style="text-align:left;"|Ethnic groups
! style="text-align:left;"|Tribes or inhabitants
! style="text-align:left;"|AA
! style="text-align:left;"|GA
! style="text-align:left;"|GG
|-
|[[Koreans|Korean]]  ||Daegu city inhabitants ||100%   || 0% ||0%
|-
|[[Chinese people|Chinese]]  ||Northern and southern Han Chinese ||80.8% || 19.2%  ||0%
|-
|[[Mongols|Mongolian]]  ||Khalkha tribe ||75.9% ||21.7% || 2.4%
|-
|[[Japanese people|Japanese]]  ||Nagasaki people ||69%  ||27.8%    || 3.2% 
|-
|[[Thai people|Thai]]||Central Thai in Bangkok ||63.3%  ||20.4%    ||16.3%
|-
|[[Vietnamese people|Vietnamese]] ||People from multiple regions ||53.6% ||39.2%    ||7.2% 
|-
|[[Dravidian people|Dravidian]]|| Inhabitants of southern India ||54.0%||17%||29%
|-
|[[Indigenous peoples of the Americas|Native American]]  || ||30%  ||40%    ||30%
|-
|[[Filipino people|Filipino]]  ||Palawan ||22.9%   ||47.9%    ||29.2% 
|-
|[[Kazakhs|Kazakh]]  || ||20% ||36.7 ||43.3%
|-
|[[Russians|Russian]]  || ||4.5% ||40.2%    ||55.3%
|-
|[[White Americans]]  ||From CEPH families without the French and Venezuelans ||1.2% ||19.5%    || 79.3%
|- 
|[[Ethnic groups of Africa|African]]  ||From various sub-Saharan nations ||0%  || 8.3%   ||91.7%  
|-
|[[African Americans]]  || ||0%  ||0%    ||100%
|}

{| class="wikitable"
|+Amino-acid conjugates of key human body odorants in sweat samples of panelists with different genotypes, determined by liquid chromatography-mass spectrometry<ref>{{cite journal | vauthors = Martin A, Saathoff M, Kuhn F, Max H, Terstegen L, Natsch A | title = A functional ABCC11 allele is essential in the biochemical formation of human axillary odor | journal = The Journal of Investigative Dermatology | volume = 130 | issue = 2 | pages = 529–540 | date = February 2010 | pmid = 19710689 | doi = 10.1038/jid.2009.254 | s2cid = 36754463 | doi-access = free }}</ref> 
! style="text-align:left;"|Genotype<br /> ABCC11
! style="text-align:left;"|Sex
! style="text-align:left;"|Ethnic population
! style="text-align:left;"|Age
! style="text-align:left;"|Net weight <br /><small> sweat (g)/2 pads</small>
! style="text-align:left;"|HMHA–Gln<br /><small>(μmol/2 pads)</small>
! style="text-align:left;"|3M2H–Gln<br /><small>(μmol/2 pads)</small>
! style="text-align:left;"|Cys–Gly conjugate
of 3M3SH <small>(μmol/2 pads)</small>
|-
|AA  || F  ||Chinese   || 27  || 2.05 || ND'  ||ND   || ND
|-
|AA  || F  || Filipino   ||33   || 2.02 || ND  ||ND   ||ND 
|-
|AA  || F  || Korean   ||35   ||1.11  || ND  ||ND   || ND
|- style="background:#efefef; color:black"
|GA  || F  ||  Filipino  ||31   || 1.47 || 1.23  || 0.17  ||Detectable, < 0.03 μmol
|- style="background:#efefef; color:black"
|GA  || F  || Thai  ||25   || 0.90 ||0.89  || 0.14   ||Detectable, < 0.03 μmol
|- style="background:#efefef; color:black"
|GA  || F  || German  || 25 ||1.64   ||0.54    ||0.10   ||Detectable, < 0.03 μmol
|-
|GG  || F  ||Filipino   ||45   ||1.74  ||0.77    ||0.13  ||Detectable, < 0.03 μmol 
|-
|GG  || F  || German   ||28   ||0.71  ||1.30    ||0.19    || 0.041 
|-
|GG  || F  || German   ||33   ||1.23  ||1.12    ||0.16    || 0.038 
|}
<small>* ND indicates that no detectable peak is found on the [M+H]+ ion trace of the selected analyte at the correct retention time. <br />* HMHA: 3-hydroxy-3-methyl-hexanoic acid; 3M2H: [[(E)-3-methyl-2-hexenoic acid]]; 3M3SH: 3-methyl-3-sulfanylhexan-1-ol.</small>

==Alterations==
Body odor may be reduced or prevented or even aggravated by using [[deodorant]]s, [[antiperspirant]]s, [[disinfectant]]s, [[underarm liners]], [[triclosan]], special soaps or foams with antiseptic plant extracts such as [[Plantago major|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 (nutrition)|diet]] as well as the other factors.<ref>{{cite web |url=http://www.mdhealthnetwork.org/BodyOder.html | archive-url = https://web.archive.org/web/20100324120612/http://www.mdhealthnetwork.org/BodyOder.html | archive-date = 24 March 2010 |title=Learn How to Fight Body Odor | work = MD Health Network |access-date=2007-07-05 }}</ref> Skin spectrophotometry analysis found that males who consumed more fruits and vegetables were significantly associated with more pleasant smelling sweat, which was described as "floral, fruity, sweet and medicinal qualities".<ref>{{Cite journal | vauthors = Zuniga A, Stevenson RJ, Mahmut MK, Stephen ID |date = January 2017 |title=Diet quality and the attractiveness of male body odor |journal=Evolution and Human Behavior |language=en |volume=38|issue=1|pages=136–143|doi=10.1016/j.evolhumbehav.2016.08.002|bibcode = 2017EHumB..38..136Z |issn=1090-5138 }}</ref>

===Industry===
As many as 90% of Americans and 92% of teenagers use antiperspirants or deodorants.<ref>{{cite news | vauthors = Pomeroy R |title=Antiperspirants Alter Your Armpit Bacteria and Could Actually Make You Smell Worse |url=http://www.realclearscience.com/blog/2014/08/antiperspirants_alter_your_armpit_bacteria_and_could_actually_make_you_smell_worse.html |work=RealClearScience |date=10 August 2014 }}</ref><ref>{{cite news | vauthors = Considine A |title=Genetically, Some of Us Never Have Body Odor, But We Still Think We're Smelly |url= https://www.vice.com/en/article/even-if-you-dont-smell-you-probably-use-deodorant/ |work=Vice |date=17 January 2013 }}</ref> In 2014, the global market for deodorants was estimated at US$13 billion with a compound annual growth rate of 5.62% between 2015 and 2020.<ref>{{Cite web|url=http://www.gosreports.com/global-deodorants-market-is-expected-to-reach-usd-17-55-billion-by-2020/|title=Global Deodorants Market is Expected to Reach USD 17.55 Billion by 2020|publisher=gosreports.com|access-date=2016-07-29|archive-date=October 28, 2016|archive-url=https://web.archive.org/web/20161028112243/http://www.gosreports.com/global-deodorants-market-is-expected-to-reach-usd-17-55-billion-by-2020/|url-status=usurped}}</ref>

==Medical conditions==
Osmidrosis or bromhidrosis is defined by a foul odor due to a water-rich environment that supports bacteria, which is caused by an abnormal increase in perspiration ([[hyperhidrosis]]).<ref name=kanlay/> This can be particularly strong when it happens in the axillary region (underarms). In this case, the condition may be referred to as axillary osmidrosis.<ref name=kanlay/> The condition can also be known medically as apocrine bromhidrosis, ozochrotia, fetid sweat, body smell, or malodorous sweating.<ref>{{cite book | vauthors = William J, Berger T, Elston D | date = 2005 | title = Andrews' Diseases of the Skin: Clinical Dermatology | edition = 10th | publisher = Saunders | page = 779 | isbn = 978-0-7216-2921-6 }}</ref><ref>{{cite book | vauthors = Freedberg IM, Eisen AZ, Austen KF, Goldsmith LA, Katz SI | title = Fitzpatrick's Dermatology in General Medicine | date = 2003 | edition = 6th | publisher = McGraw-Hill | page = 707 | isbn = 978-0-07-138076-8 }}</ref>

===Treatment===
If body odor is affecting a person’s quality of life, then seeing a primary care physician may be helpful. A doctor could recommend prescription antiperspirants containing aluminum-chloride.<ref>{{cite web |last1=Felman |first1=Adam |title=What to know about body odor |url=https://www.medicalnewstoday.com/articles/173478 |website=Medical News Today|date=November 29, 2017 }}</ref> This chemical agent helps temporarily block sweat pores which reduces the amount a person will sweat. Deodorant is another remedy for body odor. It specifically targets odor but will not reduce sweat. Deodorants are usually alcohol-based which fights off bacteria.<ref>{{cite web |title=Sweating and body odor |url=https://www.mayoclinic.org/diseases-conditions/sweating-and-body-odor/diagnosis-treatment/drc-20353898 |website=Mayo Clinic}}</ref> Most deodorants contain perfumes which also help with masking odor. If someone is experiencing severe body odor, a doctor may recommend a surgical procedure called endoscopic thoracic sympathectomy.<ref>{{cite web |title=Endoscopic thoracic sympathectomy |url=https://medlineplus.gov/ency/article/007291.htm |website=Medlineplus medical encyclopedia}}</ref> This surgery will cut nerves that control sweating. This surgery poses the risk of harming other nerves in the body. 

===Prevention===
{{How-to section|date=December 2024}}
There are a number of ways to prevent body odor. These suggestions may help with those suffering from body odor. Bathing daily with antibacterial soap helps reduce the amount of bacteria found on the skin.<ref>{{cite web |last1=Brennan |first1=Dan |title=Tips for Reducing Body Odor |url=https://www.webmd.com/skin-problems-and-treatments/reduce-body-odor |website=WebMD}}</ref> This is especially important after doing any type of physical activity. Shaving armpit hair allows for sweat to evaporate more quickly so it won’t produce an odor. Applying deodorant or antiperspirant after showering which helps kill bacteria and prevent someone from sweating is helpful. Wearing fresh and clean clothes is also very important especially if you sweat a lot. 

[[Trimethylaminuria]] (TMAU), also known as fish odor syndrome or fish malodor syndrome, is a rare metabolic disorder where trimethylamine is released in the person's sweat, urine, and breath, giving off a strong fishy odor or strong body odor.<ref>{{Cite news|url=http://www.medicalnewstoday.com/articles/173478.php|title=Body Odor: Causes, Prevention, Treatments|work=Medical News Today|access-date=2017-03-04|language=en}}</ref>

== See also ==
{{col div|colwidth=40em}}
* [[Drug resistance]]
* [[Foot odor]]
* [[Halitosis|Halitosis (bad breath)]]
* [[Old person smell]]
* [[Olfactory fatigue]]
* [[Pheromone]]
* [[Sweat gland]]
{{colend}}

== References ==
{{Reflist}}

== External links ==
* {{cite news | vauthors = Flores G |title=Immunity, smell linked |url=https://www.the-scientist.com/research-round-up/immunity-smell-linked-49417 |work=The Scientist Magazine |date=4 November 2004}}
* {{Skeptoid|id=4855|number=855|title=Sniffing for Human Sex Pheromones|date=October 25, 2022}}
{{Medical resources
|  DiseasesDB     = 28886
|  ICD10          = {{ICD10|L|75|0|l|60}}
|  ICD9           = {{ICD9|705.89}}
|  ICDO           =
|  OMIM           =
|  MedlinePlus    =
|  eMedicineSubj  = derm
|  eMedicineTopic = 597
|  MeshID         =
}}

{{Disorders of skin appendages|state=collapsed}}
{{Authority control}}

{{DEFAULTSORT:Body Odor}}
[[Category:Animal physiology]]
[[Category:Body odor| ]]
[[Category:Hygiene]]
[[Category:Immunology]]