Cocaine combined with capsaicin, an active ingredient in pepper spray, can be deadly, if research in mice is any indication. In the early 1990s, anecdotes of people dying after being doused with pepper spray puzzled researchers, until autopsies revealed many were on cocaine at the time. To look for a link between the two substances, a research team injected cocaine, capsaicin or both at once into the abdomens of several groups of about 30 mice. Injections allowed them to control the dose of capsaicin the mice received, which wouldn't have been possible if the mice were simply sprayed