Soaps and Hand Sanitizers: What Works Best Against Germs?

Sanitizers need at least 60 percent alcohol to be effective.

Feb. 5, 2013— -- In this season of the flu and other bugs like the norovirus, people are constantly told that the best and first lines of defense are hand sanitizers and soaps to get rid of as many as 400,000 germs (per hand) that travel with us every day.

But with so many choices on the drugstore shelf, what works best?

ABC News' Chief Medical Editor Dr. Richard Besser, along with six graduate students from the University of Maryland, put them to the test in the university's Food Safety Lab. They started by deliberately coating their hands with a lab liquid with thousands of E. coli bacteria -- a harmless strain. Then they got down to testing, pressing their hands to petri dishes before and after each trial, and then putting the dishes in an incubator for two days to watch the bacteria grow.

Hand sanitizers, those little bottles people use at times when they can't get to a sink, were tried first. The key with a hand sanitizer is to use enough of it. Coat the front and back of your hands, getting them wet enough that they take at least 15 seconds to dry.

We tested one sanitizer with 60 percent alcohol and one labeled "natural," containing no alcohol. The results were dramatic: the alcohol-based sanitizer showed dramatically fewer bacteria colonies in the petri dishes than the samples taken before the sanitizer was used.

The non-alcohol sanitizer's results were not as good. Alcohol-based sanitizers work because alcohol breaks up bacterial proteins, and kills them.

What about plain old soap? We tried both regular and antibacterial soap. We found they were about equally effective, and the CDC says they're about the same at preventing illness. But though the soaps might be about the same, It's how you use them that's crucial.

Studies show most of us only spend five seconds at the sink -- and that's not enough. When we tested a five-second wash, the petri dish samples from before and after washing looked virtually the same. You have to wash your hands for a full 20 seconds to really get the bugs off (to make sure you're washing for 20 seconds, sing "Happy Birthday" to yourself twice).

When it comes to fighting bacteria, hand sanitizers work well if you can't get to a sink. Look for one with at least 60 percent alcohol. But washing with any kind of soap is your best option. Soap not only does as well on bacteria as sanitizer, it gets more viruses too -- as long as you wash for long enough.