Foot odor
Encyclopedia
Foot odor is a type of body odor
that affects the feet
of humans and is generally considered to be an unpleasant smell.
s and/or sock
s with inadequate air ventilation
for many hours. Hair on the feet, especially on the toes, may contribute to the odor's intensity by adding increased surface area in which the bacteria can thrive.
Given that socks directly contact the feet, their composition can have an impact on foot odor. Polyester
and nylon
are common materials used to make socks, but provide less ventilation than cotton
or wool
do when used for the same purpose. Wearing polyester or nylon socks may increase perspiration and therefore may intensify foot odor. Because socks absorb varying amounts of perspiration from feet, wearing shoes without socks may increase the amount of perspiration contacting feet and thereby increase bacterial activities that cause odor.
. However, it can also be ammonia
-like. Brevibacteria are considered a major cause of foot odor because they ingest dead skin on the feet and, in the process, convert amino acid
methionine
into methanethiol
, which has a sulfuric aroma. The dead skin that fuels this process is especially common on the soles and between the toes. The brevibacteria is also what gives cheese
s such as Limburger, Bel Paese
, Port du Salut
, and Munster
their characteristic pungency.
Propionic acid
(propanoic acid) is also present in many foot sweat samples. This acid is a breakdown product of amino acids by Propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. The similarity in chemical structures between propionic acid and acetic acid
, which share many physical characteristics such as odor, may account for foot odors identified as being vinegar-like. Isovaleric acid (3-methyl butanoic acid) is the other source of foot odor and is a result of actions of the bacteria Staphylococcus epidermidis
, which is also present in several strong cheese types.
Bart Knols, of Wageningen Agricultural University, the Netherlands, received an "IG Nobel" prize in 2006 for showing that the female malaria
mosquito
Anopheles gambiae
"is attracted equally to the smell of limburger cheese and to the smell of human feet". Fredros Okumu, of Ifakara Health Institute in Tanzania, received grants in 2009 and 2011 to develop mosquito attractants and traps to combat malaria. He uses a blend of eight chemicals, which is four times more effective than an actual human.
Among the earliest foot deodorants were aromatic herbs such as allspice
, which nineteenth-century Russian soldiers would put in their boots.
Odor absorbers include activated charcoal foot insert wafers, such as Innofresh footwear odor absorbers.
(a mildly basic
white salt also known as baking soda, bread soda, cooking soda, bicarbonate of soda, sodium bicarb, bicarb soda, or simply bicarb). Sodium bicarbonate will create a hostile environment unsuitable for the bacteria responsible for the bad smell. Four pinches of it on each foot everyday are usually enough (two inside the sock and two on the insole of the shoe). Sometimes it might take one or two days before the shoes completely lose their old smell. Washing your feet and applying the sodium bicarbonate daily are also potentially useful solutions.
While there are a number of other remedies, sodium bicarbonate, if bought in a supermarket, costs approximately 20 times less than common odor-eaters or odor-killer powders.
Swabbing feet twice daily with isopropyl alcohol
, found at your local drug store, for two weeks is a cheap and highly effective cure. One can also periodically remove their footwear, to reduce foot moisture and thereby reduce bacterial spawn.
Some types of powders and activated charcoal insoles, such as odor eaters, have been developed to prevent foot odor by keeping the feet dry. Special cedarsoles can be recommended for this purpose because of their antibacterial characteristics. Hygiene is considered important in avoiding odor, as is avoidance of synthetic shoes/socks, and rotation of the pairs of shoes worn.
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....
that affects the feet
Foot
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws...
of humans and is generally considered to be an unpleasant smell.
Cause
The main cause is foot sweat. Sweat itself is odorless, but it creates a beneficial environment for certain bacteria to grow and produce bad-smelling substances. These bacteria are naturally present on our skin as part of the human flora. Therefore, more smell is created with factors causing more sweating, such as wearing shoeShoe
A shoe is an item of footwear intended to protect and comfort the human foot while doing various activities. Shoes are also used as an item of decoration. The design of shoes has varied enormously through time and from culture to culture, with appearance originally being tied to function...
s and/or sock
Sock
A sock is an item of clothing worn on the feet. The foot is among the heaviest producers of sweat in the body, as it is able to produce over of perspiration per day. Socks help to absorb this sweat and draw it to areas where air can evaporate the perspiration. In cold environments, socks decrease...
s with inadequate air ventilation
Ventilation (architecture)
Ventilating is the process of "changing" or replacing air in any space to provide high indoor air quality...
for many hours. Hair on the feet, especially on the toes, may contribute to the odor's intensity by adding increased surface area in which the bacteria can thrive.
Given that socks directly contact the feet, their composition can have an impact on foot odor. Polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...
and nylon
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
are common materials used to make socks, but provide less ventilation than cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
or wool
Wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....
do when used for the same purpose. Wearing polyester or nylon socks may increase perspiration and therefore may intensify foot odor. Because socks absorb varying amounts of perspiration from feet, wearing shoes without socks may increase the amount of perspiration contacting feet and thereby increase bacterial activities that cause odor.
Odor qualities
The quality of foot odor is often reported as a thick, cheesy smell. Some describe the smell like that of malt vinegarVinegar
Vinegar is a liquid substance consisting mainly of acetic acid and water, the acetic acid being produced through the fermentation of ethanol by acetic acid bacteria. Commercial vinegar is produced either by fast or slow fermentation processes. Slow methods generally are used with traditional...
. However, it can also be ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
-like. Brevibacteria are considered a major cause of foot odor because they ingest dead skin on the feet and, in the process, convert amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
methionine
Methionine
Methionine is an α-amino acid with the chemical formula HO2CCHCH2CH2SCH3. This essential amino acid is classified as nonpolar. This amino-acid is coded by the codon AUG, also known as the initiation codon, since it indicates mRNA's coding region where translation into protein...
into methanethiol
Methanethiol
Methanethiol is a colorless gas with a smell like rotten cabbage. It is a natural substance found in the blood and brain of humans and other animal as well as plant tissues. It is disposed of through animal feces. It occurs naturally in certain foods, such as some nuts and cheese...
, which has a sulfuric aroma. The dead skin that fuels this process is especially common on the soles and between the toes. The brevibacteria is also what gives cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....
s such as Limburger, Bel Paese
Bel Paese
Bel Paese is the classical poetical appellative for Italy, meaning the "Beautiful Country" in Italian, due to its mild weather, cultural heritage and natural endowment....
, Port du Salut
Port-du-Salut cheese
Port-du-Salut or Entrammes is a mild variety of smear-ripened cheese manufactured from cow's milk first made by monks in the early 18th century and still produced in monasteries throughout France....
, and Munster
Munster (cheese)
Munster or Munster-géromé, is a strong tasting, soft cheese made mainly from milk from the Vosges, between Alsace, Lorraine and Franche-Comté in France....
their characteristic pungency.
Propionic acid
Propionic acid
Propanoic acid is a naturally occurring carboxylic acid with chemical formula CH3CH2COOH. It is a clear liquid with a pungent odor...
(propanoic acid) is also present in many foot sweat samples. This acid is a breakdown product of amino acids by Propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. The similarity in chemical structures between propionic acid and acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
, which share many physical characteristics such as odor, may account for foot odors identified as being vinegar-like. Isovaleric acid (3-methyl butanoic acid) is the other source of foot odor and is a result of actions of the bacteria Staphylococcus epidermidis
Staphylococcus epidermidis
Staphylococcus epidermidis is one of thirty-three known species belonging to the genus Staphylococcus. It is part of human skin flora, and consequently part of human flora. It can also be found in the mucous membranes and in animals. Due to contamination, it is probably the most common species...
, which is also present in several strong cheese types.
Bart Knols, of Wageningen Agricultural University, the Netherlands, received an "IG Nobel" prize in 2006 for showing that the female malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
mosquito
Mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...
Anopheles gambiae
Anopheles gambiae
Anopheles gambiae is a complex of at least seven morphologically distinguishable species of mosquitoes in the genus Anopheles. This complex was recognised in the 1960s and includes the most important vectors of malaria in sub-Saharan Africa and the most efficient malaria vectors known.This species...
"is attracted equally to the smell of limburger cheese and to the smell of human feet". Fredros Okumu, of Ifakara Health Institute in Tanzania, received grants in 2009 and 2011 to develop mosquito attractants and traps to combat malaria. He uses a blend of eight chemicals, which is four times more effective than an actual human.
Extinguishment
Once foot odor has begun, it can be extinguished, or at least alleviated, by either aromatic deodorants that neutralise the odor by their own smell, or by absorbers of the odor itself.Among the earliest foot deodorants were aromatic herbs such as allspice
Allspice
Allspice, also called Jamaica pepper, pepper, myrtle pepper, pimenta, or newspice, is a spice that is the dried unripe fruit of Pimenta dioica , a mid-canopy tree native to the Greater Antilles, southern Mexico, and Central America, now cultivated in many warm parts of the world...
, which nineteenth-century Russian soldiers would put in their boots.
Odor absorbers include activated charcoal foot insert wafers, such as Innofresh footwear odor absorbers.
Prevention
Methods of extinguishment may be used even before onset of the odor as prevention. However, a very effective and cheap way to prevent foot odor is with sodium bicarbonateSodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...
(a mildly basic
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
white salt also known as baking soda, bread soda, cooking soda, bicarbonate of soda, sodium bicarb, bicarb soda, or simply bicarb). Sodium bicarbonate will create a hostile environment unsuitable for the bacteria responsible for the bad smell. Four pinches of it on each foot everyday are usually enough (two inside the sock and two on the insole of the shoe). Sometimes it might take one or two days before the shoes completely lose their old smell. Washing your feet and applying the sodium bicarbonate daily are also potentially useful solutions.
While there are a number of other remedies, sodium bicarbonate, if bought in a supermarket, costs approximately 20 times less than common odor-eaters or odor-killer powders.
Swabbing feet twice daily with isopropyl alcohol
Isopropyl alcohol
Isopropyl alcohol is a common name for a chemical compound with the molecular formula C3H8O. It is a colorless, flammable chemical compound with a strong odor...
, found at your local drug store, for two weeks is a cheap and highly effective cure. One can also periodically remove their footwear, to reduce foot moisture and thereby reduce bacterial spawn.
Some types of powders and activated charcoal insoles, such as odor eaters, have been developed to prevent foot odor by keeping the feet dry. Special cedarsoles can be recommended for this purpose because of their antibacterial characteristics. Hygiene is considered important in avoiding odor, as is avoidance of synthetic shoes/socks, and rotation of the pairs of shoes worn.