Heat, infrared and the body's response
TRPV1
TRPV1, transient receptor potential vanilloid 1, is an ion channel on sensory nerve endings that opens above roughly 43 °C and also responds to capsaicin, the pungent compound in chilli, and to acid. It is why heat past a certain point is felt as burning pain.
Also called transient receptor potential vanilloid 1, capsaicin receptor, vanilloid receptor
TRPV1 belongs to the thermoTRP family of ion channels. It sits in the membrane of pain-sensing sensory neurons, and when it opens it lets positive ions into the cell, firing the nerve. It is unusual in integrating several different kinds of stimulus through the same channel: noxious heat above about 43 °C, capsaicin, low pH, and certain inflammatory mediators. That convergence is why a chilli tastes hot and why inflamed tissue becomes more sensitive to warmth. Its identification as the capsaicin receptor was foundational work in sensory neuroscience, recognised by the 2021 Nobel Prize in Physiology or Medicine.
Why it appears in a sauna glossary. TRPV1 is the reason the boundary between comfortably warm and painfully hot is sharp, and roughly in the same place for everyone. A client’s report that the sauna is too hot is a nerve signal rather than a matter of taste. A first-session range of 30 to 37 °C sits well below the threshold — though a humid sauna raises skin temperature faster than a dry one at the same setting.
Why it matters here
It is why a client saying the sauna is too hot is reporting a physiological signal rather than a preference. The right response is to lower the temperature or end the session.