question: Why does the sweat from our armpits stink?
comment: Sweat doesn’t smell but the bacteria that builds up in a warm damp place does which is why the armpit can still smell even when there’s no sweat.
passages: Human perspiration of all types is largely odorless until its organic components are fermented by bacteria that thrive in hot, humid environments. The human underarm is among the most consistently warm areas on the surface of the human body, and sweat glands readily provide moisture containing a proportion of organic matter, which when excreted, has a vital cooling effect. When adult armpits are washed with alkaline pH soap, the skin loses its protective acid mantle (pH 4.5 - 6), raising the skin pH and disrupting the skin barrier. Many bacteria are adapted to the slightly alkali environment within the human body, so they can thrive within this elevated pH environment. this makes the skin more than usually susceptible to bacterial colonization. Bacteria on the skin feed on the waste proteins and fatty acids in the sweat from the apocrine glands and on dead skin and hair cells, releasing trans-3-methyl-2-hexenoic acid in their waste, which is the primary cause of body odor. 
   Axilla
  
  The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint where the arm connects to the shoulder. It also provides the under-arm sweat gland. 
  
  In humans, the formation of body odor happens mostly in the axillary region. These odorant substances serve as pheromones which play a role related to mating. The underarm regions seem more important than the genital region for body odor which may be related to human bipedalism.
  
  Section::::Structure.
  
  Section::::Structure.:Boundaries.
  
  Anatomically, the boundaries of the "axilla" are:
   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. Areas that produce excessive sweat usually appear pink or white, but, in severe cases, may appear cracked, scaly, and soft.
  
  Section::::Causes.
   In humans, the formation of body odors is caused by factors such as diet, gender, health, and medication, but the major contribution comes from bacterial activity on skin gland secretions. Humans have three types of sweat glands; eccrine sweat glands, apocrine sweat glands and sebaceous glands. Eccrine sweat glands are present from birth, while the two latter become activated during puberty. Among the different types of human skin glands, the body odor is primarily the result of the apocrine sweat glands, which secrete the majority of chemical compounds needed for the skin flora to metabolize it into odorant substances. This happens mostly in the axillary (armpit) region, although the gland can also be found in the areola, anogenital region, and around the navel. In humans, the armpit regions seem more important than the genital region for body odor which may be related to human bipedalism. The genital and armpit regions also contain springy hairs which help diffuse body odors.
   Section::::Background.
   BULLET::::- Sweat glands are distributed all over the body except nipples and outer genitals. Although the nipples do have the mammary glands, these are known as "modified sweat glands".
  
  BULLET::::- Sebaceous glands are typically found in the opening shaft of hair. They are not on the palms of the hands or the soles of the feet. These glands secrete an antibacterial moisture known as "sebum fluid". The sebum also softens the hands. The secretion activity is related to hormonal release. If acne is occurring, it is because these gland ducts are blocked.
   Section::::Examples.:Cowbirds.
   Body odor is influenced by the actions of the skin flora, including members of "Corynebacterium", which manufacture enzymes called lipases that break down the lipids in sweat to create smaller molecules like butyric acid. Greater bacteria populations of "Corynebacterium jeikeium" are for example found more in the armpits of men whereas greater population numbers of "Staphylococcus haemolyticus" are found in the armpits of women. This causes male armpits to give off of a rancid/cheese-like smell whereas female armpits give off a more fruity/onion-like smell. "Staphylococcus hominis" is also known for producing thioalcohol compounds that contribute to odors. These smaller molecules smell, and give body odor its characteristic aroma. Propionic acid (propanoic acid) is present in many sweat samples. This acid is a breakdown product of some amino acids by propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. Because propionic acid is chemically similar to acetic acid with similar characteristics including odor, body odors may be identified as having a vinegar-like smell by certain people. Isovaleric acid (3-methyl butanoic acid) is the other source of body odor as a result of actions of the bacteria "Staphylococcus epidermidis", which is also present in several strong cheese types.
   Some people can develop a sweat allergy. The allergy is not due to the sweat itself but instead to an allergy-producing protein secreted by bacteria found on the skin. Tannic-acid has been found to suppress the allergic response along with showering.
  
  Section::::Causes.:Hyperhidrosis.
   Section::::Clinical significance.:Lymphogenic spread of breast cancer.
  
  Breast cancer typically spreads via lymphatic vessels to the lymph nodes found in the axilla.
  
  Section::::Clinical significance.:Axillary intertrigo.
  
  Excessive perspiration can result in axillary intertrigo. Intertrigo is an inflamed skin condition caused by heat, friction, and moisture. A warm, wet underarm may accommodate the growth of pathogenic bacteria, yeasts, and fungi. The condition is responsible for rash-like symptoms, pustules, or chronic itching or burning in the underarm. Axillary intertrigo is common among those who work in hot environments.
  
  Section::::See also.
  
  BULLET::::- Deodorant
  
  BULLET::::- Perspiration
  
  BULLET::::- Popliteal fossa or "knee pit"
   Body odor encompasses axillary (underarm) odor and foot odor. It is caused by a combination of sweat gland secretions and normal skin microflora. In addition, androstane steroids and the ABCC11 transporter are essential for most axillary odor. Body odor is a complex phenomenon, with numerous compounds and catalysts involved in its genesis. Secretions from sweat glands are initially odorless, but preodoriferous compounds or malodor precursors in the secretions are transformed by skin surface bacteria into volatile odorous compounds that are responsible for body malodor. Water and nutrients secreted by sweat glands also contribute to body odor by creating an ideal environment for supporting the growth of skin surface bacteria.
   Body odor is also a potentially embarrassing grooming issue and a common reason for trimming or removing body hair. While it’s not the hair itself that smells, body odor is caused by bacteria that grow in wet conditions when air is standing still. Hair reduces the amount of air exchange and traps sweat so it can support the growth of odor-causing bacteria.
   The human body produces perspiration (sweat) via two types of sweat gland: eccrine sweat glands which cover much of the skin and produce watery odourless sweat, and apocrine sweat glands in the armpits and groin, which produce a more oily "heavy" sweat containing a proportion of waste proteins, fatty acids and carbohydrates, that can be metabolized by bacteria to produce compounds that cause body odor. In addition the vagina produces secretions which are not a form of sweat but may be undesired and also masked with deodorants.
   Another aspect of bacteria is the generation of body odor. Sweat is odorless however several bacteria may consume it and create byproducts which may be considered putrid by man (as in contrast to flies, for example, that may find them attractive/appealing).
  
  Several examples are:
  
  BULLET::::- "Propionibacteria" in adolescent and adult sebaceous glands can turn its amino acids into propionic acid.
  
  BULLET::::- "Staphylococcus epidermidis" creates body odor by breaking sweat into isovaleric acid (3-methyl butanoic acid).
  
  BULLET::::- "Bacillus subtilis" creates strong foot odor.
  
  Section::::Skin defenses.
  
  Section::::Skin defenses.:Antimicrobial peptides.
   Trichobacteriosis axillaris
  
  Trichobacteriosis axillaris is a superficial bacterial colonization of the hair shafts in sweat gland–bearing areas, such as the armpits and the groin. It is a trivial disease of worldwide occurrence that is believed to be caused by the genus "Corynebacteria".
  
  The condition has been called extensively "trichomycosis axillaris" in the literature, but because it is a bacterial infection and not a fungal infection, it should be called "trichobacteriosis".
  
  Section::::Presentation.
   Of note, the parts of the body which are commonly shaved and also commonly treated with deodorants, such as the armpits, contain substantial deposits of subcutaneous fat. Shaving cuts would be extremely unlikely to penetrate sufficiently beyond the very outer layers of the skin, for much if any product to enter the bloodstream.
  
  Section::::Health effects.:Aluminum.:Alzheimer's disease.
   Diaphoresis is a non-specific symptom or sign, which means that it has many possible causes. Some causes of diaphoresis include physical exertion, menopause, fever, ingestion of toxins or irritants, and high environmental temperature. Strong emotions (anger, fear, anxiety) and recall of past trauma can also trigger sweating.
   There are three types of sweat glands: eccrine, apocrine, and apoeccrine. Apocrine glands are primarily responsible for body malodor and, along with apoeccrine glands, are mostly expressed in the axillary (underarm) regions, whereas eccrine glands are distributed throughout virtually all of the rest of the skin in the body, although they are also particularly expressed in the axillary regions, and contribute to malodor to a relatively minor extent. Sebaceous glands, another type of secretory gland, are not sweat glands but instead secrete sebum (an oily substance), and may also contribute to body odor to some degree.
   The term "underarm" typically refers to the outer surface of the axilla. However, the terms are sometimes used interchangeably in casual contexts. Colloquially, "underarm " refers to the hollow beneath the junction of the arm and shoulder.
  
  The term oxter is used in the Scots language and in Ireland instead of "axilla".
  
  Section::::Society and culture.:Tickling.
  
  The underarm can be a ticklish area, possibly due to the number of nerves it contains. Some people find this area to be particularly unpleasant when tickled.
  
  Section::::Society and culture.:Underarm hair.
   As many as 90% of Americans and 92% of teenagers use antiperspirants or deodorants. In 2014, the global market for deodorants was estimated at 13.00 billion USD with a compound annual growth rate of 5.62% between 2015 and 2020.
  
  Section::::Medical conditions.
  
  The condition can be known medically as bromhidrosis, apocrine bromhidrosis, osmidrosis, ozochrotia, fetid sweat, body smell, or malodorous sweating.
   Underarm hair wicks the moisture away from the skin and aids in keeping the skin dry enough to prevent or diminish bacterial colonization. The hair is less susceptible to bacterial growth and therefore reduces bacterial odor. The apocrine sweat glands are inactive until puberty, which is why body odor often only becomes noticeable at that time.
  
  Deodorant products work in one of two ways - by preventing sweat from occurring, or by allowing it to occur but preventing bacterial activity that decomposes sweat on the skin.
  
  Section::::History.
  
  Section::::History.:Early deodorants.
   Staging a patient's axillary hair will allow the physician to track the child's development longitudinally.
  
  The evolutionary significance of human underarm hair is still debated. It may naturally wick sweat or other moisture away from the skin, aiding ventilation. Colonization by odor-producing bacteria is thereby transferred away from the skin (see skin flora).
  
  Section::::Cultural attitudes.
   Many other trace elements are also excreted in sweat, again an indication of their concentration is (although measurements can vary fifteenfold) zinc (), copper (), iron (), chromium (), nickel (), and lead (). Probably many other less-abundant trace minerals leave the body through sweating with correspondingly lower concentrations. Some exogenous organic compounds make their way into sweat as exemplified by an unidentified odiferous "maple syrup" scented compound in several of the species in the mushroom genus "Lactarius". In humans, sweat is hypoosmotic relative to plasma (i.e. less concentrated). Sweat is found at moderately acidic to neutral pH levels, typically between 4.5 and 7.0.
   The infection is diagnosed by close examination of the hair shafts where brown to yellow material called concretions are seen. There is usually an associated rancid odour. A microscopic examination can confirm the diagnosis, but this is rarely needed.
  
  Some patients with excessive sweating present the so-called corynebacterial triad, that is, the simultaneous presence of trichobacteriosis axillaris, erythrasma, and pitted keratolysis.
  
  Section::::Treatment.
  
  No specific therapeutic studies on trichobacteriosis are available.
   Perspiration
  
  Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals.
  
  Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distributed over much of the body.
  
presuppositions: Sweat has a bad smell. Sweat stinks.
corrections: The bacteria that grow in sweaty places have a bad smell. Sweat doesn't smell, the smell is from bacteria that builds up in a warm damp place.
raw_presuppositions: Sweat has a bad smell. Sweat stinks.
raw_corrections: The bacteria that grow in sweaty places have a bad smell. Sweat doesn't smell, the smell is from bacteria that builds up in a warm damp place.