Foot Odor - Odor Qualities

Odor Qualities

The quality of foot odor is often reported as a thick smell. Some describe the smell like that of malt vinegar. 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 cheeses such as Limburger, Bel Paese, Port du Salut, Pálpusztai 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.

Other implicated micro-organisms include Micrococcaceae, Corynebacterium and Pityrosporum.

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.