Why We Itch

Dec 10, 2018

We’re all familiar with an itchy bug bite, maybe the torture of poison ivy or chicken pox. But what if that kind of itching went on and on?

It’s a problem called chronic itch and it's of particular to Brian Kim, also known as the Itch Doctor. (That’s his Twitter handle.) He’s co-director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis. 

But what evolutionary benefit could we possibly get by itching? 

“It signals to us that there are mosquitoes in the environment,” Kim said. And, as we know, mosquitos can give us diseases like malaria or Eastern equine encephalitis.

“That's something that we would, through time, want to have been able to detect,” he said.

Without the urge to scratch, the itch would not fulfill its evolutionary mission of getting us to swat the mosquito or expel the toxin in our skin.

But why not just feel pain? Why do we have to itch?

If everything felt like a bee sting, we would be afraid of going outside, Kim explained. It would be hard to get food and water.

“There are situations in which we need to know something's wrong -- we don't want to really stick around -- but we still need one to get whatever we need to get done and get out.”

Chronic itch is a problem that affects anywhere from 15 to 20 percent of the population at any given time,  and can severely damage quality of life, Kim said.

There are very few treatments for chronic itch, but some do exist.

“Recently…we were able to identify a new pathway that regulates itch,” Dr. Kim said. “Serendipitously there was a drug already on the market for another condition, rheumatoid arthritis. This drug actually can work really well for chronic itch.”