Itch experts: Scratching really makes it worse

Posted at 5:44 PM, Oct 30, 2014

Do you feel an itch, right now, working its way down the back of your neck?

Scratching temporarily relieves that itch, but can also make it worse. Now researchers at the Center for the Study of Itch at Washington University in St. Louis – yes, that’s real – know why.

“The itch is important in sensation. Everyone scratches, right?” said Zhou-Feng Chen, director of the Itch Center. “ Everyone suffers from chronic itch at one point or another during their lifetime.”

Scratching alleviates an itch by creating pain – your nails damage the skin, after all. But the brain doesn’t like to experience pain, Zhou-Feng said, so it sends out a pleasure hormone that reduces the pain, called serotonin.

Unfortunately, serotonin can “jump the tracks” in the spinal cord and excite another set of nerves to start another itch cycle. Chen said his lab is the first to discover that.

“On one hand you want to create more pain to control the itch but on the other hand the brain does opposite things because it doesn’t want there to be too much pain,” Chen said.

To find this out, Chen and other Washington University researchers bred mice who can’t produce their own serotonin. When Chen tried to make the mice itch, they didn’t scratch much. But when they were given a dose of serotonin, they started to scratch.

The study was published Thursday in the journal Neuron.

So why even study itching, let alone establish a center for it, as Washington University did in 2011?

Itching is a survival mechanism to alert animals to threats, like parasites or changes in the environment. Itching can result from serious diseases of the skin, liver, kidneys or drug side effects, Chen said.

Learning about how an itch works could lead the the development of drugs to alleviate those symptoms, which often send people to a dermatologist.

“Chronic itching is a huge problem that’s been underreported,” Chen said. “It hasn’t been fully appreciated how much people suffer.”

Gavin Stern is a national digital producer for the Scripps National Desk. Follow him on twitter at@GavinStern or email him at