Socks can acquire a foul odor due to prolonged wearing on feet. Their odor, which is complex and remains the object of study, is a mixture of
ammonia,
fatty acids (in particular,
isovaleric acid), and
lactic acid. Odorous socks are a strong attractant for some animals, including dogs and mosquitos. They have proven useful in controlling the behaviour of these animals. Although the odour of smelly socks is often associated with
feet, it arises independently of contact with human feet in various foodstuffs, such as dairy products, cheeses, sausages and
fish sauce, and is naturally present in several plants. The smell has also been noted in building and automotive air treatment systems, where it is described as "jock socks odour" or "dirty socks syndrome". Several technologies have been developed to incorporate materials into sock textiles which reduce or eliminate the strong smell. The intense smell commonly results from bacterial action upon sweat which accumulates due to confining footwear. It has also presented itself as a problem among users of
prosthetics. Smelly socks may be a source of air contamination in aircraft and dwellings. Their distinctive
odour is commonly used as a reference. A 1996
Popular Mechanics article describes "jock socks odour" complaints as one of the magazine's most frequent queries with regard to automotive air conditioning systems, attributing it to
fungal growth within the auto. The term "Dirty Sock Syndrome" is used to describe unpleasant odours that arise in building heating and cooling systems. High-efficiency
heat pumps in the southeastern US have been noted as frequent offenders. The odour is a diagnostic feature of a serious medical condition,
Isovaleric acidemia. A widespread consumer perception of the odour in the medication
metformin, frequently used to treat
Type 2 diabetes, may have contributed to patient refusals of the treatment. A test of
olfactory abilities deemed useful in Japan employs detection of "sweaty socks", along with two other odours, as a useful metric of these abilities. When fresh,
alkyl nitrites or "
poppers", smell
fruity, but when stale their aroma seems like smelly socks.
Solutions Several technologies have been developed to address the problem by modifying the composition of sock materials. Compounds which cause socks to smell intensively include: •
butyric acid, which smells like
rancid butter •
dimethyl disulphide, which smells like onions •
dimethyl trisulphide •
2-heptanone, which smells like bananas •
2-nonanone, which smells like fat, fruit or flowers •
2-octanone, which smells like apples In February 1997,
The Daily Mirror reported that a new fabric had been invented by British scientists to eliminate smelly socks.
Disinfectant treatments such as
silver nanoparticles may be applied to socks to prevent them from smelling. The
United States Air Force Academy issued a 2009 request to vendors that included socks incorporating antimicrobial silver yarn technology. This technology has encountered some opposition; a study conducted by researchers at
Arizona State University examined the possibility that the silver particles could be released when the socks were washed, posing environmental concerns. In 2000, the
University of California announced a joint venture with private companies to develop socks that would reduce the problem by incorporating compounds, a relatively stable form of
chlorine. In 2005
Dow Corning proposed the incorporation of
alkoxysilanes as a preventive measure. Researchers reported, in 2011, on a technique to permanently block the development of pathogenic germs, which can cause odour in socks and other clothing. A team led by
Jason Lockli of the
University of Georgia reported in the
American Chemical Society's
Applied Materials and Interfaces that the anti-microbial treatment of "smelly socks" could "offer low cost protection for healthcare facilities, such as hospitals." Their strong odour will also attract other dangerous wild animals such as
bears. Because this smell is so effective at attracting mosquitos, its use has been explored for mosquito control in places where
malaria is prevalent. An imitation foot odour has been synthesised at the
University of Wageningen. The synthetic odour is then used to bait traps which attract the mosquitos and so divert them from biting people. The synthetic mixture of
ammonia,
fatty acids, and
lactic acid is effective but not as good as real sweaty socks. The composition of the authentic smell is still being analysed to determine the remaining active ingredients. Dogs are strongly attracted to the scent of socks that have been worn by humans. They may
self-medicate themselves during attacks of
separation anxiety by focusing on these items. The attraction is used in
dog training, where the odorous socks may serve as a distractant or as a lure during
crate training. Smelly socks have been used to repel deer. Benefits include they are cheap and accessible, require little effort to put out each morning, and are quite effective at keeping deer out of one's flower garden.
Other uses The smell of dirty socks was the most unpleasant of the smells provided in the movie
Polyester which featured
Odorama in the form of
scratch and sniff cards. At
Fort Siloso in Singapore, the liquid scent of smelly socks is part of the exhibition which provides tourists with a sensory impression of its historical use during WW2. The plant
white plume grevillea (
Grevillea leucopteris) has long white flowers whose stink resembles that of smelly socks, causing the plant to be known as "smelly socks grevillea" or "old socks". Another plant with a similar smell and name is
clary sage (
Salvia sclarea). The herb
valerian has a musty smell of this sort too. Mushrooms of the genus
Amanita often have a strong odor which may also seem like that of smelly socks. Some people experience erotic arousal from smelling well worn socks as a
fetish. 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. Those aroused by smelling socks may be aroused only by a certain type of sock, those worn by a particular person or type of person, or in specific scenarios, such as being dominated or instructed to smell socks. Smelly socks are favoured for use as a component in the making of powerful charms or spells, especially in
voodoo or magic of African origin. They may be worn around the neck as a cure for a
cold. Smelly socks were used as the basis for a marketing campaign for
British Knights sneakers. Viewers were invited to send in their socks which would then be assessed for smell by a panel of judges which included a dog. == Sizes ==