Shocker: Advertising health claims are often misleading. In this case, it looks like most of the products that tout near-perfect germ-killing abilities are getting those results in trials that aren't exactly designed to mimic real-world conditions. When a University of Ottawa microbiologist ran a more realistic demonstration for Canadian schoolchildren, he turned up VERY different results.
Three popular sanitizers killed between 46% and 60% of microbes on the students' hands, far short of 99.99%. Bugs that aren't killed by sanitizers aren't necessarily more dangerous than those that are. But the more that remain, the greater the chance of infection, doctors say.
The ad writers also benefit from regulations that allow them to claim 99.9% effectiveness without actually killing 99.9% of all germs, all the time. Instead, representative samples can stand in, and there's room for do-overs in the lab, if the first test doesn't work.
Wall Street Journal: Kills 99.9% of Germs—Sometimes
Maggie Koerth-Baker is the science editor at BoingBoing.net. She writes a monthly column for The New York Times Magazine and is the author of Before the Lights Go Out, a book about electricity, infrastructure, and the future of energy. You can find Maggie on Twitter and Facebook.