Why and how do body parts itch? Why does it feel good to scratch an itch?

Pruritus (itchy skin)

What exactly is an itch, and why do we get itchy? — Today You Should Know

How long does an itch last if you don't scratch it? - Quora

An Allergist Explains Why You Might Have Itchy Skin All Over, Even Though You Don't Have a Rash

Serotonin Drives Vicious Cycle of Itching and Scratching

What Causes Itching? - Scientific Reasons Behind Why We Itch

How to Relieve Your Dog's Itchy Skin · The Wildest

Why is scratching your inner ear so amazing? - Quora

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Why does scratching inside the ear feel good? - Quora

Why does scratching your head feel so damn good?, by LW, Sharing Science

Don't scratch the itch: Scientists find substance that could be key to stopping the sensation, The Independent