Question: sometimes when the your skin gets burnt you dont feel it straight away but after a few seconds you feel a reaction why dont we feel it straight away?

Dalya Soond answered on 14 Jun 2011:

You might not feel a burn on your hand immediately if you are foolish enough to stick it in a fire because the nerves there are unmyelinated. Myelin is a coating on many nerves that allows signals to run through them to the brain very quickly. Once in the signal is in the brain, you can feel the pain physically and psychologically. Without the myelin, it will take slightly longer for the message to get to your brain.

Sunburn is slightly different. I actually didn’t know this until you asked (so thanks), but the pain and redness from a sunburn is actually caused by the immune response. By over-exposing yourself to the UV rays of the sun, you are basicly zapping your cells to death. The immune system then comes in to clear up the mess. Some of the chemicals the white blood cells make act on your pain receptors. But it takes a while for 1) your cells to die after UV exposure 2) the immune cells to notice 3) the cells to get into your skin and 4) the cells to give off these chemicals.