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Drowning out one signal with another

Why Does Scratching Feel So Good?

Itch has its own nerves, and scratching works by shouting over them with a signal your brain prefers.

Itch has its own nervefibresVery slow, and only inthe skinScratching adds astronger signalWhich crowds the itchout
You are not removing the itch. You are jamming it.

  1. Step 1 of 5

    Itch is not a mild pain.

    Pain Makes you withdrawItch Makes you scratch — adifferent system

    It travels on its own fibres, at its own speed, and produces its own urge: pain makes you pull away, itch makes you scratch. They are separate senses.

  2. Step 2 of 5

    Its fibres are astonishingly slow.

    A sharp pain signaltens of metres asecondAn itch signalabout half ametre a second

    Itch signals crawl along at around half a metre a second — about a hundred times slower than a sharp pain. That is why an itch creeps up on you.

  3. Step 3 of 5

    Only skin can itch.

    Skin Full of itch fibresInside Can hurt, but cannotitch

    There are no itch fibres in your muscles, bones or organs. Your liver can hurt, but it cannot itch — because itching is a warning about the surface.

  4. Step 4 of 5

    Scratching adds a louder signal.

    Scratching addsmild pain The spinal cordprioritises itover the itch

    The mild pain of scratching travels a different, faster route and the spinal cord gives it priority, so much less of the itch reaches your brain.

  5. Step 5 of 5

    Which is why it comes back worse.

    You scratch The itch isjammed Chemicalsreleased — itreturns worse

    The jamming lasts only while you scratch, and the scratching itself releases chemicals that provoke more itch. The relief is real but it is borrowed.

    Itch is thought to have evolved as an insect and parasite alarm — which is why it lives only in the skin, and why watching someone else scratch makes you itch.

The short version

Itch has its own slow nerves, and scratching feels good because mild pain crowds the itch signal out at the spinal cord.

Try it yourself

Cool an itchy patch with a cold spoon instead of scratching. Cold uses the same crowding trick without provoking more itch.

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