Bodily Functions Explained: Itch & Scratch (Get Science)


– An irritant triggers
skin neurons to send an alert. A scratch is born. Here’s what’s happening. A human has 22 square feet
of skin. Each square inch has about
a thousand nerve endings. 5% to 20% of those receptors can translate
something foreign on your skin into an itch signal. Nerve fibers speed that signal
to the spinal cord, which propels it
to the brain, which sends fingernails
to unseat the invader. Sometimes an itch
is triggered internally. In these cases,
nothing is worst for an itch than scratching. It can even spawn
a vicious cycle. Scratching blocks the itch by distracting
the brain with pain. The pain triggers
a release of serotonin, which blocks the pain
that blocked the itch, and the loop starts again. In these cases,
a gentle rub or slap should replace
the classic scratch.