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You know you shouldn’t scratch an itch. It feels oh-so-good in the moment, but once you stop, the itch is even itchier than before. Why the vicious itch-scratch cycle? A new study published in the journal Neuron may shed light on the mystery.

Catherine DiBenedetto
November 03, 2014

You know you shouldn’t scratch an itch. It feels oh-so-good in the moment, but once you stop, the itch is even itchier than before. Why the vicious itch-scratch cycle? A new study published in the journal Neuron may shed light on the mystery.

When you scratch, you experience a small amount of pain, which temporarily distracts you from the itchy sensation. Those pain signals trigger the brain to release serotonin, a neurochemical that dulls the pain. But it turns out serotonin can also amp up itchiness.

“As serotonin spreads from the brain to the spinal cord, we found the chemical can ‘jump the tracks,’ moving from pain-sensing neurons to nerve cells that influence itch intensity,” lead author Zhou-Feng Chen, PhD, said in a statement.

Chen is the director of Washington University School of Medicine’s Center for the Study of Itch (naturally). For this experiment, he and his colleagues bred mice that couldn’t produce serotonin, then injected them with a substance that causes itchiness. They found that those mice scratched less than normal mice. But when the genetically modified mice were given the itchy injection and a serotonin injection, they scratched just as much as the regular rodents. The researchers suspect serotonin has the same effect on humans, too.

Just reading this story is probably making you itchy. So what's a person to do when the urge to scratch strikes? Cold can help deaden an itch. Try applying an ice pack or a cool, wet washcloth to the affected spot.

If that doesn’t do the trick, an oatmeal bath could help soothe your skin. Drugstores sell colloidal oatmeal that will dissolve in the tub. Or you can make your own solution: Blend or process 1 cup of uncooked oats until you have a fine powder to sprinkle it into a warm (but not hot) bath.

To find out more about why people get itchy skin, check out this info from the American Academy of Allergy, Asthma & Immunology.

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