How come scratching an itch makes it even worse?

Zhou-Feng Chen of the Washington University of St. Louis’ Center for the Study of Itch finally found the answer. (Of course there's a Center for the Study of Itch.

Scratching an itch is probably one of the sweetest gratifications of nature. But there’s one down side, scratching just makes the itch even worse and now scientists finally know why.
Just like lightning and thunder, itching and scratching will be forever linked. And up until know scientists didn’t really know all that much about itching, why we do it and what evolutionary purpose it serves. Because come on, besides the fact that it can give a short relive of the itch the aftermath is just even worse.

Damn that feels good

So what is an itch? Well it’s a cousin of pain, but it is not pain in and of itself. This was proven back in the late 1980s when German researchers artificially made people super itchy by stimulating histamine production – an itch-producing substance. Even though the test subject became extremely itchy, they did not report being in any more pain. And brings us to the new scientific discovery, because while itching isn’t pain, scratching certainly causes pain, and that’s the key.

Due to scratching the brain ramps up the production of serotonin which influences the itch sensitivity

Zhou-Feng Chen of the Washington University of St. Louis’ Center for the Study of Itch – yes this really is a thing – researched the pathway that causes scratching to cause more itching. He found out that when you scratch the brain will receive pain signals and as a result it will ramp up the production of serotonin – which among many other things can modulate pain. But serotonin also can influence itch sensitivity.

This is what happens when you're scratching an itch

But what can you do about it? Well although this is a cool new finding it’s not good news for anyone hoping that we can finally figure out how to stop those mosquito bites from itching. This is due to the fact that serotonin is an incredibly important neurotransmitter that is associated with all sorts of things such as mood, appetite, sleep and pain. Screwing with serotonin levels would probably do more damage than it's worth.
So, for now, the only option to treat those itches would be some chamomile lotion