Foot odor

Foot odor (or foot odour) is a type of body odor that affects the feet of humans. It is sometimes considered to be an unpleasant smell, but can also be the target of foot fetishism, more specifically as a form of olfactophilia.[1]

It is one of the most widespread forms of olfactophilia: In a 1994 study, 45% of those with a foot fetish were found to be aroused by smelly socks and/or feet.[2]

Causes

The main cause is foot sweat (also see focal hyperhidrosis). Sweat itself is odorless; however, it creates a beneficial environment for certain bacteria to grow, producing odorous substances. These bacteria are naturally present on our skin as part of the human flora. The front part of the foot produces the most sweat.[3]

The smell is exacerbated by factors that increase sweating, such as wearing closed-toe shoes. Socks can trap foot hair, especially on the toes, and may contribute to odor intensity by increasing surface area on which bacteria can thrive.

Given that socks directly contact the feet, their composition can affect foot odor. Synthetic materials like polyester and nylon afford less ventilation to the foot than do cotton or wool, leading to increased perspiration and odor, although they can also reduce incidence of blisters by wicking away perspiration. Many synthetic socks are treated with chemicals to help reduce odor.[4]

Wearing closed-toe shoes (e.g., ballet flats or pumps) without socks leads to accumulation of sweat, dead skin cells, dirt, and oils, further contributing to bacterial growth. Momentarily slipping off shoes whenever feet start to feel "hot" or sweaty can help prevent odor.

Odor qualities

The quality of foot odor is often described as being thick and resembling that of cheese, malt vinegar, or ammonia.

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 methionine into methanethiol, a colorless gas with a distinctive sulfuric aroma. The dead skin that fuels this process is especially common on the sole and between the toes. Brevibacteria also give such cheeses as Limburger, Bel Paese, Port Salut, Pálpusztai and Munster their characteristic pungency.[5]

Propionic acid (propanoic acid), a breakdown product of Propionibacteria amino acid metabolism in adolescent and adult sebaceous gland ducts, is also present in many foot sweat samples. The similarity between the chemical structures of propionic acid and acetic acid may account for the tendency of foot odors to be identified as smelling like vinegar.

Isovaleric acid (3-methyl butanoic acid), another other source of foot odor, is produced by Staphylococcus epidermidis, a bacterial species normally resident on human skin[6] and present in several strong-smelling varieties of cheese.

Other implicated microorganisms include Micrococcaceae, Corynebacterium and Pityrosporum.[7]

Bart Knols of Wageningen Agricultural University in the Netherlands received a 2006 "Ig Nobel Prize"[8] for demonstrating that the female Anopheles gambiae mosquito, known for transmitting malaria, is "attracted equally to the smell of Limburger cheese and to the smell of human feet".[9] Fredros Okumu, of the Ifakara Health Institute in Tanzania, received grants in 2009 and 2011 to develop mosquito attractants and traps to combat malaria.[10] He used a blend of eight chemicals four times more effective than actual human secretions.[11]

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. A foot file or pumice stone can be used to remove dead skin cells.[12] Dirty feet and dirty socks, instead of clean, dry socks changed frequently can contribute to odor. Socks that are made of synthetic materials are more prone to becoming smelly than natural or blended fabrics, such as a blend of cotton and polyester.

Sodium bicarbonate is used as an inexpensive home remedy for the prevention of foot odor. However, the extent of the antimicrobial effect on the odor-causing bacteria is unclear. A solution of 10% household bleach in 90% water kills the odor-causing bacteria. A brush can be used to clean between the toes. Swabbing feet twice daily with isopropyl alcohol is another home remedy.

Some powders and activated charcoal insoles, such as odor eaters, have been developed with the purpose of preventing foot odor by keeping the feet dry. Special cedarsoles and socks with silver fibers with antibacterial characteristics are available.

Bamboo fabric socks are naturally anti-microbial, anti bacterial and moisture wicking, cutting odor and abating athlete's foot.

See also

References

  1. ↑ "The History of Footwear - Foot Fetish and Shoe Retifism". Retrieved 28 May 2018.
  2. ↑ Patricia B. Sutker; Henry E. Adams (2001), Comprehensive handbook of psychopathology, p. 762, ISBN 978-0-306-46490-4
  3. ↑ "INTERACTION OF SILVER NITRATE WITH COMMERCIALLY AVAILABLE COTTON SOCKS; RELATIONSHIP TO THE ANTIBACTERIAL ACTION OF SILVER IONS" (PDF). 21 February 2015. Retrieved 31 March 2015.
  4. ↑ Smelly Feet (Foot Odor) ePodiatry.com
  5. ↑ Betsy's Bacteria Wheaton College Quarterly
  6. ↑ Ara, Katsutoshi; Masakatsu Hama; Syunichi Akiba; Kenzo Koike; Koichi Okisaka; Toyoki Hagura; Tetsuro Kamiya; Fusao Tomita (April 2006). "Foot odor due to microbial metabolism and its control". Canadian Journal of Microbiology. 52 (4): 357–364. doi:10.1139/w05-130. ISSN 0008-4166. PMID 16699586. Retrieved 2012-05-09.
  7. ↑ Kanlayavattanakul, M; Lourith N (August 2011). "Body malodours and their topical treatment agents". International Journal of Cosmetic Science. 33 (4): 298–311. doi:10.1111/j.1468-2494.2011.00649.x. PMID 21401651.
  8. ↑ "2006 Nobel Prize Announcements". The Nobel Prize Internet Archive.
  9. ↑ Bart G.J. Knols (November 9, 1996), "On Human Odour, Malaria Mosquitoes, and Limburger Cheese", The Lancet, 348: 1322, doi:10.1016/S0140-6736(05)65812-6, PMID 8909415
  10. ↑ McLaughlin, Michael (July 15, 2011) [July 13, 2011]. "Scientists: Stinky Sock Smell Helps Fight Malaria". Huffington Post.
  11. ↑ Susannah Palk (2 August 2011). "'Dirty sock smell' lures mosquitoes to a sticky end". CNN. Retrieved 14 October 2018.
  12. ↑ "The solution - Stinkyfeet". Stinkyfeet. Retrieved 2016-02-12.
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