# Foot odor

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{{Short description|Type of body odor that affects the feet of humans}}
{{Use American English|date=March 2021}}
{{Use mdy dates|date=March 2021}}
{{pp-pc1|small=yes}}
{{Refimprove|date=May 2013}}

'''Foot odor''' (also spelled '''foot odour''') or '''bromodosis''' is a type of [body odor](/source/body_odor) that affects the [feet](/source/foot) of [human](/source/human)s.

==Causes==
The main cause is foot [sweat](/source/Perspiration) (also see [focal hyperhidrosis](/source/focal_hyperhidrosis)). Sweat itself is odorless, but it creates a beneficial environment for certain bacteria to grow, producing odorous substances. These bacteria are naturally present on human skin as part of the [human microbiome](/source/human_microbiome). The front part of the foot produces the most sweat.<ref>{{cite web|url=http://www.ijisr.com/sites/default/files/issues-pdf/034.pdf|title=INTERACTION OF SILVER NITRATE WITH COMMERCIALLY AVAILABLE COTTON SOCKS; RELATIONSHIP TO THE ANTIBACTERIAL ACTION OF SILVER IONS|date=21 February 2015|access-date=31 March 2015|archive-date=August 27, 2019|archive-url=https://web.archive.org/web/20190827012526/http://www.ijisr.com/sites/default/files/issues-pdf/034.pdf|url-status=dead}}</ref>

The smell is exacerbated by factors that increase sweating, such as wearing closed-toe shoes. Sports footwear such as [sneakers](/source/sneakers) is often heavily padded inside which provides a perfect environment to trap moisture and allow the bacteria to thrive. Socks can trap [foot hair](/source/foot_hair), especially on the [toe](/source/toe)s, and may contribute to odor intensity by increasing [surface area](/source/surface_area) on which bacteria can thrive.{{cn|date=July 2017}}

Given that [sock](/source/sock)s directly contact the feet, their composition can affect foot odor. [Synthetic materials](/source/synthetic_fiber) like [polyester](/source/polyester) and [nylon](/source/nylon) afford less [ventilation](/source/breathability) to the foot than do [cotton](/source/cotton) or [wool](/source/wool), leading to increased perspiration and odor, although they can also reduce incidence of [blister](/source/blister)s by [wicking](/source/Capillary_action) away perspiration. Many synthetic socks are treated with chemicals to help reduce odor.<ref>{{Cite web|title=Smelly foot (Foot Odor) - Information from ePodiatry|url=http://www.epodiatry.com/smelly-foot.htm|access-date=2023-01-02|website=www.epodiatry.com}}</ref>

Wearing closed-toe shoes (e.g., [ballet flat](/source/ballet_flat)s or pumps) without socks leads to accumulation of sweat, dead [skin cells](/source/keratinocytes), dirt, and [oils](/source/sebaceous_gland), further contributing to bacterial growth.

A different cause of foul odor from the feet is [onychomycosis](/source/Onychomycosis), a fungal infection of the toenails.<ref>{{cite web|title=Nail fungus|website=Mayo Clinic|date=15 May 2024|url=https://www.mayoclinic.org/diseases-conditions/nail-fungus/symptoms-causes/syc-20353294}}</ref><ref>{{cite web|title=Causes and Treatments of Toenail Fungus|website=LifeMD|date=31 January 2023|url=https://lifemd.com/learn/toenail-fungus-onychomycosis-causes-and-treatments}}</ref>

==Odor qualities==
''[Brevibacteria](/source/Brevibacteria)'' are considered a major cause of foot odor because they ingest dead skin on the feet and, in the process, convert the [amino acid](/source/amino_acid) [methionine](/source/methionine) into [methanethiol](/source/methanethiol), a colorless gas with a distinctive [sulfur](/source/sulfur)ic aroma. The dead skin that fuels this process is especially common on the [sole](/source/Sole_(foot)) and [between the toes](/source/interdigital_webbing). Brevibacteria also give such [cheese](/source/cheese)s as [Limburger](/source/Limburger), [Bel Paese](/source/Bel_Paese_(cheese)), [Port Salut](/source/Port_Salut), [Pálpusztai](/source/P%C3%A1lpusztai) and [Munster](/source/Munster_(cheese)) their characteristic [pungency](/source/pungency).<ref>{{Cite journal
| title= Characterization of aerobic non-lipophilic coryneforms from human feet
| vauthors = Anthony RM, Noble WC, Pitcher DG | journal= Clinical and Experimental Dermatology | issn = 0307-6938
| year =  1992 
| volume= 17 | number=2 
| pages =  102–105 |publisher=Blackwell Scientific Publications
| doi = 10.1111/j.1365-2230.1992.tb00174.x | pmid=1516232
| s2cid = 33517719 }}</ref>{{rp|103}}

[Isovaleric acid](/source/Isovaleric_acid) (3-methyl butanoic acid), another source of foot odor, is produced by ''[Staphylococcus epidermidis](/source/Staphylococcus_epidermidis)'', a bacterial species normally [resident on human skin](/source/skin_flora)<ref>{{Cite journal| doi = 10.1139/w05-130| issn = 0008-4166| volume = 52| issue = 4| pages = 357–364| last = Ara| first = Katsutoshi|author2=Masakatsu Hama |author3=Syunichi Akiba |author4=Kenzo Koike |author5=Koichi Okisaka |author6=Toyoki Hagura |author7=Tetsuro Kamiya |author8=Fusao Tomita | title = Foot odor due to microbial metabolism and its control| journal = Canadian Journal of Microbiology| date = April 2006| pmid=16699586| citeseerx = 10.1.1.1013.4047}}</ref> and present in several strong-smelling varieties of cheese.<ref>{{cite journal
| title=Isovaleric acid is mainly produced by Propionibacterium freudenreichii in Swiss cheese
| author1= Thierry, Anne
| author2=Richoux, Romain
| author3= Kerjean, Jean-René
| journal=International Dairy Journal
| year=2004
| volume= 14 | issue= 9
| pages=801–807
| doi=10.1016/j.idairyj.2004.02.002
| s2cid= 85336899
| url= https://hal.archives-ouvertes.fr/hal-02264923/file/Thierry04_IDJ-iC5_1.pdf
}}</ref>

Other implicated [microorganisms](/source/microorganisms) include [Micrococcaceae](/source/Micrococcaceae), ''[Corynebacterium](/source/Corynebacterium)'' and ''[Pityrosporum](/source/Pityrosporum)''.<ref>{{Cite journal | title=Body malodours and their topical treatment agents | last=Kanlayavattanakul | first=M |author2=Lourith N | 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>

[Bart Knols](/source/Bart_Knols) of [Wageningen Agricultural University](/source/Wageningen_Agricultural_University) in the [Netherlands](/source/Netherlands) received a 2006 "[Ig Nobel Prize](/source/Ig_Nobel_Prize)"<ref>{{cite web |url=https://improbable.com/ig/winners/?amp=1#ig2006 |title=The 2006 Ig Nobel Prize Winners
| series = Past Ig Winners
|website= improbable.com|date=August 2006
}}</ref> for demonstrating that the female ''[Anopheles gambiae](/source/Anopheles_gambiae)'' [mosquito](/source/mosquito), known for transmitting [malaria](/source/malaria), is "attracted equally to the smell of [Limburger](/source/Limburger) cheese and to the smell of human feet".<ref>{{citation |title=On Human Odour, Malaria Mosquitoes, and Limburger Cheese |author= Bart G.J. Knols |journal= The Lancet |volume= 348 |issue= 9037 |date= November 9, 1996 |page=1322|doi=10.1016/S0140-6736(05)65812-6 |pmid=8909415|s2cid= 12571262 }}</ref> [Fredros Okumu](/source/Fredros_Okumu), of the [Ifakara Health Institute](/source/Ifakara_Health_Institute) in [Tanzania](/source/Tanzania), received grants in 2009 and 2011 to develop [mosquito attractant](/source/mosquito_control)s and [trap](/source/insect_trap)s to combat malaria.<ref>{{cite news |url=http://www.huffingtonpost.com/2011/07/13/stinky-socks-smell-malaria_n_896819.html |title= Scientists: Stinky Sock Smell Helps Fight Malaria |orig-year=July 13, 2011 |date=July 15, 2011 | work=Huffington Post |first=Michael |last=McLaughlin}}</ref> He used a blend of eight chemicals four times more effective than actual human secretions.<ref>{{cite news |language = en |author = Susannah Palk |url = http://edition.cnn.com/2011/WORLD/africa/07/26/tanzania.malaria.socks/index.html |archive-url = https://web.archive.org/web/20110726223123/http://edition.cnn.com/2011/WORLD/africa/07/26/tanzania.malaria.socks/index.html |url-status = dead |archive-date = July 26, 2011 |title = 'Dirty sock smell' lures mosquitoes to a sticky end |publisher = CNN |date = 2 August 2011 |access-date = 14 October 2018}}</ref>

==Prevention==
Maintaining good foot hygiene is the best way to prevent foot odor as it eliminates odor causing bacteria and removes dead skin cells as well as [sebum](/source/sebum). A foot file, [pumice stone](/source/pumice_stone) or chemical treatment, such as an [Alpha hydroxy acid](/source/Alpha_hydroxy_acid) containing foot peel preparation, can be used to remove dead skin cells.<ref>{{Cite web|title = The solution - Stinkyfeet|url = http://www.stinkyfeet.org/the-solution/|website = Stinkyfeet|access-date = 2016-02-12|language = en-US|archive-date = May 14, 2021|archive-url = https://web.archive.org/web/20210514110237/http://www.stinkyfeet.org/the-solution/|url-status = dead}}</ref><ref>{{cite web |last1=VELASCO |first1=PIA |title=Read This Before You Try the 'Baby Foot' Peel Craze |url=https://www.goodhousekeeping.com/beauty-products/a38129/baby-foot-peel-safety/ |website=Good Housekeeping |access-date=19 October 2019|date=2019-03-25 }}</ref> Using antibacterial soap to wash feet daily; keeping feet dry by changing socks daily and wearing cotton or wool instead of synthetic fibers can also help reduce moisture build-up. Using medicated insoles and foot powder can also help.<ref>{{cite web |title=How to stop smelly feet |url=https://www.nhs.uk/live-well/healthy-body/how-to-avoid-smelly-feet/ |website=NHS UK |publisher=National Health Service |access-date=19 October 2019|date=2018-04-26 }}</ref>

==Management==
In some cases, medical intervention may be needed to treat the bacterial or fungal infection with a topical antibacterial or fungicide.<ref>{{cite journal |last1=Fernández-Crehuet |first1=P |last2=Ruiz-Villaverde |first2=R |title=Pitted keratolysis: an infective cause of foot odour. |journal=Canadian Medical Association Journal |date=21 April 2015 |volume=187 |issue=7 |pages=519 |doi=10.1503/cmaj.140809 |pmid=25712956 |pmc=4401600 }}</ref><ref>{{cite web |title=ATHLETE'S FOOT (TINEA PEDIS) |url=https://www.summitmedicalgroup.com/library/pediatric_health/hhg_athlete_foot/ |website=Summit Medical Group |access-date=19 October 2019}}</ref>

==As a paraphilia==
Foot odor is one of the most widespread forms of olfactophilia;<ref>{{cite web|url=http://podiatry.curtin.edu.au/fetish.html#freud|archive-url=https://web.archive.org/web/20071018035445/http://podiatry.curtin.edu.au/fetish.html#freud|url-status=dead|archive-date=18 October 2007|title=The History of Footwear - Foot Fetish and Shoe Retifism|access-date=28 May 2018}}</ref> in a 1994 study, 45% of those with a [foot fetish](/source/foot_fetish) were found to be aroused by [smelly socks](/source/smelly_socks) and/or feet, but most importantly by the intensity of the smell produced by such bacteria.<ref>{{citation |title=Comprehensive handbook of psychopathology |author1=Patricia B. Sutker |author2=Henry E. Adams |url=https://books.google.com/books?id=uEx84FQPYoAC|page=762 |year=2001 |publisher=Springer |isbn=978-0-306-46490-4}}</ref>

==See also==
* [Body odor](/source/Body_odor)
* [Body odour and sexual attraction](/source/Body_odour_and_sexual_attraction)
* [Shoe](/source/Shoe)
* [Smelly socks](/source/Smelly_socks)

==References==
{{Reflist|2}}

{{DEFAULTSORT:Foot Odor}}
Category:Foot
Category:Hygiene
Category:Body odor

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Adapted from the Wikipedia article [Foot odor](https://en.wikipedia.org/wiki/Foot_odor) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Foot_odor?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.