Scientists experimenting in mice may have found the culprit: A molecule used by the heart is pulling double duty, sending a message to the spinal cord that ultimately produces that familiar tickle on our skin.

The finding elevates itch—previously thought to be a mild form of pain—to a separate phenomenon, with "its own dedicated landline to the brain," study co-author Mark Hoon, a molecular geneticist at the National Institute of Dental and Craniofacial Research in Bethesda, Maryland, said in a statement.

And because mice and people share similar biology, the scientists suspect that people also have this circuit.

The discovery could also someday identify a way to block the molecule from producing itching—a potentially life-changing intervention for millions of