From Harvard Medical School:
Using the zebrafish as an animal model, researchers have discovered that the body uses hydrogen peroxide to sound the alarm when a tissue has been injured. As a direct result of this hydrogen-peroxide red alert, white blood cells come to the aid of the wounded site.
Prior research has indicated that white blood cells produce hydrogen peroxide to kill bacteria, but never before has it been know to act as a kind of “first responder” that alerts healing cells to bodily trauma. This is important because scientists know very little about how tissue detects that it’s been damaged, and what sorts of signals it sends as a result. Although these findings occurred in zebrafish, they offer new ways to begin thinking about certain human conditions, like asthma, which are associated with elevated levels of hydrogen peroxide and white blood cells in the affected areas.