The researchers also demonstrated that scratching prompts pain-sensing neurons to release a chemical known as substance P, which triggers mast cells: cells involved in the immune system, causing inflammation and itchiness via neutrophils.

Scratching isn’t just a bad habit — it’s an immune defense mechanism. While it fuels inflammation, it also helps fight infections by drawing immune cells to the skin. Scientists have uncovered how this paradoxical process works,

Mice that were free to scratch their itchy ears saw the number of immune cells go up and levels of infection-causing bacteria decline