You mother probably told you that if you scratch an itch, it always makes it worse. Well now science has proven your mother right, literally.
Researchers from Washington University School of Medicine in St. Louis revealed results from a study that proved that scratching triggers the brain into releasing serotonin, which, in turn, increases the sensation of itch.
The team started with the basic knowledge that scratching creates a sensation of pain in the skin. That pain temporarily alleviates the sensation of itching because the spinal cord sends signals to the brain indicating pain instead of signals that indicate itching.
This causes the body to release serotonin, a neurotransmitter that helps the body control that pain. However, as serotonin travels from the brain to the spinal cord, it sometimes moves from those neurons associated with sensing pain to neurons that intensify itch.
In other words, when you scratch an itch, it often makes it itch even more.
This is the first time that scientists have linked seratonin with itching.
In their experiments, researchers bred mice without serotonin. They gave this group of mice, plus regular mice, injections of a substance that makes the skin itch. The mice without serotonin scratched far less than their normal counterparts.
"So this fits very well with the idea that itch and pain signals are transmitted through different but related pathways," says Zhou-Feng Chen, PhD, director of Washington University's Center for the Study of Itch. "Scratching can relieve itch by creating minor pain. But when the body responds to pain signals, that response actually can make itching worse."
However, you can't just block serotonin in the human body. It's necessary for everything from mood regulation to aging to growth and bone health. It's also one of the key components in the body that controls pain, something the human body requires for survival.
So researchers looked for something else that might be altered to prevent itching: the receptors that tell serotonin to send itch signals.
In a second experiment, researchers gave mice the itching substance, but also something that activates serotonin receptors. They eventually learned that one particular receptor, called 5HT1A, was responsible for telling the serotonin to intensify itching.
Researchers hope that this study helps people who suffer from chronic itching, but there is still much they don't understand about the sensation. Until then, the best advice is if you're itching, don't scratch.
Obviously, that's probably easier said than done.
