Neuroscientists have identified a previously unknown neural circuit that tells the brain when to stop scratching an itch. The discovery, made in mice at a leading biophysics lab, reveals how the nervous system balances relief and self-harm during itching. The findings were presented May 10, 2026, at the Biophysical Society meeting.
This neural switch acts like a built-in brake, preventing excessive scratching that could damage the skin. Researchers found that specific neurons in the spinal cord activate after a few seconds of scratching, sending a „stop” signal to the brain. Without this mechanism, scratching could continue uncontrollably, leading to injury. The study sheds light on how sensory feedback loops regulate instinctive behaviors.
The team used optogenetics and live imaging to track neuron activity in mice exposed to itch-inducing substances. When the animals began scratching, spinal cord neurons called LP5 cells became active. These cells connect to the brainstem and appear to monitor movement patterns linked to scratching. After several seconds, they fired strongly, coinciding with the end of scratching bouts.
Dr. Elena Torres, lead researcher, said, „We’ve long known scratching relieves itch, but not what stops it. Now we see the body has a precise off-switch.” In mice with silenced LP5 neurons, scratching lasted up to five times longer than normal. The behavior stopped only when skin damage occurred—suggesting the brain relies on this signal to prevent harm.
The LP5 pathway responds specifically to scratch-like motions, not general touch or pain. This indicates the nervous system treats scratching as a unique behavior with dedicated control circuits. The signal strength increased with scratch duration, suggesting a cumulative feedback mechanism.
Why do some people scratch until they bleed? The new findings suggest faulty LP5 signaling might be to blame. If the stop signal is weak or delayed, scratching could spiral out of control—common in conditions like eczema or psoriasis.
Current treatments focus on reducing itch intensity but don’t address the stop mechanism. „We might need drugs that boost the stop signal, not just block the itch,” Torres explained. Early tests show activating LP5 cells reduces scratching even when itch signals remain.
Researchers now plan to look for similar circuits in humans using non-invasive imaging. If confirmed, therapies could one day target this pathway directly.
What is the „stop scratching” signal? It’s a neural circuit involving LP5 cells in the spinal cord that activate during scratching and tell the brain to stop. It prevents prolonged skin contact that could cause injury.
Could this help treat skin conditions? Yes. If the stop signal is impaired in chronic itch disorders, drugs that strengthen it could reduce harmful scratching, even if the itch remains.
Was this study done in humans? No. The research was conducted in mice. Human equivalents are suspected but not yet confirmed.