Perspiration
Perspiration, also known as sweat, is the fluid secreted by sweat glands in the skin of mammals.[1]
"Sweat" redirects here. For other uses, see Sweat (disambiguation).Perspiration
Sweating, hidrosis, diaphoresis
Two types of sweat glands can be found in humans: eccrine glands and apocrine glands.[2] The eccrine sweat glands are distributed over much of the body and are responsible for secreting the watery, brackish sweat most often triggered by excessive body temperature. Apocrine sweat glands are restricted to the armpits and a few other areas of the body and produce an odorless, oily, opaque secretion which then gains its characteristic odor from bacterial decomposition.
In humans, sweating is primarily a means of thermoregulation, which is achieved by the water-rich secretion of the eccrine glands. Maximum sweat rates of an adult can be up to 2–4 litres (0.53–1.06 US gal) per hour or 10–14 litres (2.6–3.7 US gal) per day, but is less in children prior to puberty.[3][4][5] Evaporation of sweat from the skin surface has a cooling effect due to evaporative cooling. Hence, in hot weather, or when the individual's muscles heat up due to exertion, more sweat is produced. Animals with few sweat glands, such as dogs, accomplish similar temperature regulation results by panting, which evaporates water from the moist lining of the oral cavity and pharynx.
Although sweating is found in a wide variety of mammals,[6][7] relatively few (apart from humans, horses, some primates and some bovidae) produce sweat in order to cool down.[8] In horses, such cooling sweat is created by apocrine glands[9] and contains a wetting agent, the protein latherin which transfers from the skin to the surface of their coats.[10]
Signs and symptoms[edit]
Sweat contributes to body odor when it is metabolized by bacteria on the skin. Medications that are used for other treatments and diet also affect odor. Some medical conditions, such as kidney failure and diabetic ketoacidosis, can also affect sweat odor.
Other functions[edit]
Antimicrobial[edit]
Sweat may serve an antimicrobial function, like that of earwax or other secretory fluids (e.g., tears, saliva, and milk). It does this through a combination of glycoproteins that either bind directly to, or prevent the binding of microbes to, the skin and seem to form part of the innate immune system.[30]
In 2001, researchers at Eberhard-Karls University in Tübingen, Germany, isolated a large protein called dermcidin from skin. This protein, which could be cleaved into other antimicrobial peptides, was shown to be effective at killing some species of bacteria and fungi that affect humans, including Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. It was active at high salt concentrations and in the acidity range of human sweat, where it was present at concentrations of 1–10 mg/ml.[31][32]
Society and culture[edit]
Artificial perspiration[edit]
Artificial skin capable of sweating similar to natural sweat rates and with the surface texture and wetting properties of regular skin has been developed for research purposes.[33][34] Artificial perspiration is also available for in-vitro testing, and contains 19 amino acids and the most abundant minerals and metabolites in sweat.
Diagnostics[edit]
There is interest in its use in wearable technology. Sweat can be sampled and sensed non-invasively and continuously using electronic tattoos, bands, or patches.[35] However, sweat as a diagnostic fluid presents numerous challenges as well, such as very small sample volumes and filtration (dilution) of larger-sized hydrophilic analytes. Currently the only major commercial application for sweat diagnostics is for infant cystic fibrosis testing based on sweat chloride concentrations.
