Why scratching makes an itch worse
Have an itch that you can’t seem to ease? It’s not your imagination; it’s your brain. In a new study, researchers have found the brain releases serotonin when you scratch yourself so it’s not painful. However, the serotonin also activates neurons in the spinal cord to re-trigger that itching sensation.
Scientists at the Washington University School of Medicine in St. Louis genetically engineered mice so that they did not have the ability to make serotonin. The researchers then injected a substance into the mice to make their skin itch. At first they didn’t scratch much, but once serotonin was injected, their normal response to itching occurred.
While the research was performed on mice, it is believed the same chemical exchange happens in humans. It’s unclear how, but researchers discovered that serotonin can switch from signaling pain-sensing neurons to nerve cell neurons in the spinal cord that set off the itching sensation.
The researchers said they hope the findings, published in the journal Neuron, can be used to help people with chronic itching. Treatment could include breaking the signal between serotonin and the spinal cord neurons involved in the itching sensation.