Itching. How interesting a medical topic can it be? Turns out, very very:

Now various phenomena became clear. Itch, it turns out, is indeed inseparable from the desire to scratch. It can be triggered chemically (by the saliva injected when a mosquito bites, say) or mechanically (from the mosquito’s legs, even before it bites). The itch-scratch reflex activates higher levels of your brain than the spinal-cord-level reflex that makes you pull your hand away from a flame. Brain scans also show that scratching diminishes activity in brain areas associated with unpleasant sensations.

But some basic features of itch remained unexplained—features that make itch a uniquely revealing case study. On the one hand, our bodies are studded with receptors for itch, as they are with receptors for touch, pain, and other sensations; this provides an alarm system for harm and allows us to safely navigate the world. But why does a feather brushed across the skin sometimes itch and at other times tickle? (Tickling has a social component: you can make yourself itch, but only another person can tickle you.) And, even more puzzling, how is it that you can make yourself itchy just by thinking about it?

The article describes cases of chronic itching that weren’t solved by cutting the nerve endings. Neuroscientists studying this phenomenon have linked it to phantom limb disorders and various issues often classified as psychiatric. This has lead to radical theories on our brain’s use of external stimuli. Atul Gawande, the author, compares it to a car: a sensor reports a problem, so you fiddle in the engine. Nothing fixes it so eventually you treat the driver, when it’s actually the sensor itself that’s broken.

How do you treat this? I won’t spoil it, but the research does have some practical applications. Highly recommended, and very well written – I’ve just ordered a cheap copy of the author’s first book.

Warning one: it’s a little gruesome, and I’ll be impressed if you don’t get any wide-eyed pauses, with an optional ‘oh my god’.

Warning two: Metafilter commenters report this article causing massive itching. I got a very mild outbreak, but some have it much worse…