Why does getting certain chemicals in cuts hurt?

Question

More specifically, shampoo. What are the mechanics of detecting a noxious chemical stimulus in terms of which receptors recognise what, how do they do it, and how is this information relayed to the nerve cells? Why is the pain (and so signal, I presume) larger if one is having a *hot* shower at the time?

Answer 1

The receptors in the body that respond to pain, called nociceptors, respond to a variety of stimuli - including increasing levels of pressure (mechanoreceptors), chemicals (chemoreceptors), and extremes in temperature (heat and cold). Because some nociceptors respond to chemicals, certain chemicals, particularly acidic chemicals, can significantly increase pain in a wound, as they increase the responses of the pain receptors. Also, as some of those nociceptors respond to temperature, heat in the area of a wound can do a number of things, including leading to more nociceptors being activated (by the heat directly), and by bringing more immune cells and their inflammatory chemicals into the area of the wound (heat increases blood flow, whereas cold decreases blood flow).