A new research has cracked the answers to as why scratching makes one itch more and has observed that scratching causes the brain to release serotonin, which intensifies the itch sensation. The study conducted at Washington University School of Medicine in St. Louis, showed that findings in mice are same vicious cycle of itching and scratching is thought to occur in humans.

Zhou-Feng Chen, PhD, director of Washington University's Center for the Study of Itch, said that the problem was that when the brain geot those pain signals, it responded by producing the neurotransmitter serotonin to help control that pain but as serotonin spreads from the brain into the spinal cord, they found the chemical could "jump the tracks" moving from pain-sensing neurons to nerve cells that influenced itch intensity.

The researchers bred a strain of mice that lacked the genes to make serotonin. When those genetically engineered mice were injected with a substance that normally makes the skin itch, the mice didn't scratch as much as their normal littermates but when the genetically altered mice were injected with serotonin, they scratched as mice would be expected to in response to compounds designed to induce itching.

Chen said that they always have wondered why this vicious itch-pain cycle occurs. Their findings suggest that the events happen in this order. First, one scratch, and that causes a sensation of pain then one make more serotonin to control the pain but serotonin does more than only inhibit pain. The study is published in the journal Neuron.