question: Why does skin turn red when exposed to hot water?
comment: Heat makes the blood vessels in your skin dilate. This brings the blood closer to the surface of your skin than normal, enough to be easily seen through your skin.
passages: Hot roots
  
  Hot roots is a term used by hair stylists to explain the condition brought about by applying an artificial pigment to the hair, whereby the roots (the sections of the hair follicles closest to the scalp) are noticeably warmer in color (more red/orange) than the ends of the hair. This can happen for a few reasons, but the two most likely causes are explained below.
   Section::::Hypothesis.:Social conditioning.
  
  Folklore, mythology and literature associate red with fertility, and women are thought to have worn the equivalent of a red lipstick as early as 10,000 B.C. and so sexual receptiveness and red may be a result of social conditioning. However, this social conditioning may have originated for biological and evolutionary reasons, and is simply an extension of our primal instincts. The human genitals, such as the vulva normally have hair that would hide any coloured skin underneath.
  
  Section::::Evidence for and against.
   Commonly referred to as the sex flush, vasocongestion (increased blood flow) of the skin can occur during all four phases of the human sexual response cycle. Studies show that the sex flush occurs in approximately 50–75% of females and 25% of males, yet not consistently. The sex flush tends to occur more often under warmer conditions and may not appear at all under lower temperatures.
   Red skin
  
  Red skin may refer to:
  
  BULLET::::- Redskin, a term referring to Native Americans in the United States and Canada's First Nations
  
  BULLET::::- Flushing (physiology), to temporarily become markedly red in the face or other areas of the skin
  
  BULLET::::- Erythroderma, an inflammatory disease of the skin that causes a red appearance along with scaling
  
  BULLET::::- Erythema, a symptom describing redness of skin or mucous membranes caused by increased blood flow in the superficial capillaries
  
  BULLET::::- Topical steroid withdrawal, also known as red burning skin
  
  Section::::See also.
  
  BULLET::::- Redskin (disambiguation)
   Hot flashes, a common symptom of menopause and perimenopause, are typically experienced as a feeling of intense heat with sweating and rapid heartbeat, and may typically last from two to thirty minutes for each occurrence, ending just as rapidly as they began. The sensation of heat usually begins in the face or chest, although it may appear elsewhere such as the back of the neck, and it can spread throughout the whole body. Some women feel as if they are going to faint. In addition to being an internal sensation, the surface of the skin, especially on the face, becomes hot to the touch. This is the origin of the alternative term "hot flush", since the sensation of heat is often accompanied by visible reddening of the face. Excessive flushing can lead to rosacea.
   Heat also effects the viscosity of a fluid inside a capillary. An increase in heat decreases the viscosity of the lumenal fluid. A good example of this action can be observed in the human body during exercise. When a human is exercising, there is an increase in the metabolic rate inside the muscles, creating an increase in heat production. The increase in heat is detected by thermoreceptors, a type of sensory receptor located at various points in body. These receptors send a signal to the brain that tells the body to dilate the blood vessels, including capillaries. This creates a visible change in the number of vessels on the skin. This allows for heat transfer via convection to occur.
   Hot hardness
  
  In materials engineering and metallurgy, hot hardness or red hardness (when a metal glows a dull red from the heat) corresponds to hardness of a material at high temperatures. As the temperature of material increases, hardness decreases and at some point a drastic change in hardness occurs. The hardness at this point is termed the "hot" or "red" hardness of that material. Such changes can be seen in materials such as heat treated alloys.
   Maude Barlow an environmental activist, head of the Council of Canadians, and founder of the Blue Planet Project has used the term 'hot stain' in regard to water resources. In 2005, Maude Barlow received Sweden's Right Livelihood Award.
  
  Section::::Water resources.
   Once the hot water has been added, the mate is ready for drinking, and it may be refilled many times before becoming "lavado" (washed out) and losing its flavor. When this occurs, the mound of "yerba" can be pushed from one side of the gourd to the other, allowing water to be added along its opposite side; this revives the mate for additional refillings and is called ""reformar o/el mate"" (reforming the mate).
  
  Section::::Etiquette.
   At Sandrine's house Esther has a shower and Sandrine, coming in to deliver Esther's clean clothes, sees the extra cuts Esther made to her leg. Sandrine is shocked. Esther is again indifferent to her loved-ones concerns. Later they talk about work, Sandrine is fed-up with work and wants to move up in the company they both belong to.
   In 17th-century New England, red was associated with adultery. In the 1850 novel by Nathaniel Hawthorne, The Scarlet Letter, set in a Puritan New England community, a woman is punished for adultery with ostracism, her sin represented by a red letter 'A' sewn onto her clothes.
   In one version of the story, Aphrodite injured herself on a thorn from a rose bush and the rose, which had previously been white, was stained red by her blood. The third century BC poet Euphorion of Chalcis remarked in his "Hyacinth" that "Only Cocytus washed the wounds of Adonis". According to Lucian's "De Dea Syria", each year during the festival of Adonis, the Adonis River in Lebanon (now known as the Abraham River) ran red with blood.
  
  Section::::Cult.
   Heated bath
  
  A heated bath is used in the laboratory to allow a chemical reaction to occur at an elevated temperature. 
  
  The heated bath is a fluid placed in an open (metal) pot. Water and silicone oil are the most commonly used fluids. A water bath is used for temperatures up to 100 °C. An oil bath is employed for temperatures over 100 °C.
   Red heat
  
  The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which was known to be best for the work.
  
  Section::::Chapman.
  
  According to Chapman's "Workshop Technology", the colours which can be observed in steel are:
  
  Section::::Stirling.
  
  In 1905, Stirling Consolidated Boiler Company published a slightly different set of values:
  
  Section::::See also.
  
  BULLET::::- Color temperature
   A second set of methodological tools involves physiological measures such as heart rate, galvanic skin responses (sweating) or muscle activity. Heart rate is used as a measure of whether an orienting response has occurred. When people show an aroused response, their heart rate decelerates for a few seconds before returning toward their baseline. Likewise, an increase in skin conductance is evidence of an aroused response. Thus, the combined evidence of heart rate deceleration and an increase in skin conductance provides convergent evidence that an orienting response (OR) has occurred.
   Among both sexes, the excitement phase results in an increase in heart rate, breathing rate, and a rise in blood pressure. A survey in 2006 found that sexual arousal in about 82% of young females and 52% of young males arises or is enhanced by direct stimulation of nipples, with only 7–8% reporting that it decreased their arousal. Vasocongestion of the skin, commonly referred to as the sex flush, will occur in approximately 50-75% of females and 25% of males. The sex flush tends to occur more often under warmer conditions and may not appear at all under cooler temperatures.
   Section::::Treatment.
  
  Section::::Treatment.:Hormone replacement therapy.
   Hsp27 is a major phosphoprotein during women's contractions. Hsp27 functions in small muscle migrations and appears to serve an integral role.
  
  Section::::Function.:Immunity.
  
  Function of heat-shock proteins in immunity is based on their ability to bind not only whole proteins, but also peptides. The affinity and specificity of this interaction is typically low.
   BULLET::::- Arteriolar vasodilation occurs. The smooth muscle walls of the arterioles relax allowing increased blood flow through the artery. This redirects blood into the superficial capillaries in the skin increasing heat loss by convection and conduction.
  
  Section::::In hot and humid conditions.
   game, a popular kids game.)
  
  Then they found a hot spring where monkeys were bathing (sometimes monkeys in Japan bathe in the hot spring). Shinnosuke bathed among the monkeys.
   Section::::Initiation.:Flux.
   Al-Sukhnah means "the Warm" in Arabic, and is so named because of the nearby sulphur springs. As late as the early 20th century, the inhabitants of the village would bathe in the hot springs.
  
  Section::::History.
   Many of the patination processes involve boiling the metal in the modifying solution, and the final colour can depend on the duration of the boiling period, which may range from minutes to hours. Suaka, for example, may advance from a light brown after 2–4 hours, to orange-brown after 6 hours, to red towards 10 hours. 
   Section::::History.:20th and 21st century.
  
  From the 8th century until the early 20th century, the most important scarlet pigment used in western art was vermilion, made from the mineral cinnabar. It was used, along with red lake pigments, by artists from Botticelli and Raphael to Renoir. However, in 1919 commercial production began of an intense new synthetic pigment, cadmium red. made from cadmium sulfide and selenium. The new pigment became the standard red of Henri Matisse and the other important painters of the 20th century.
   Refractory period (physiology)
  
  Refractoriness is the fundamental property of any object of autowave nature (especially excitable medium) not to respond on stimuli, if the object stays in the specific "refractory state". In common sense, refractory period is the characteristic recovery time, a period of time that is associated with the motion of the image point on the left branch of the isocline formula_1 (for more details, see also Reaction-diffusion and Parabolic partial differential equation).
  