That's great advice, but we wanted more information. What should we wash with? Is antibacterial soap better than regular soap? And do hand sanitizers really work?
"Good Morning America" put them all to the test. We went to the University of Maryland, a world leader in food safety and microbiology, and did a small, informal test in which we basically washed our hands until they were raw.
Caution: Not all soaps and sanitizers are created equal.
"Good Morning America" enlisted Jianghong Meng and his intrepid University of Maryland graduate students to do the experiment with us.
That's right. We deliberately put E. coli bacteria on our hands to see which products would wash it off. The E. coli we used for our experiment was a harmless strain, not the deadly E. coli 0-157.
After each test, we swabbed our hands to see if there was any bacteria left that would transfer to these special incubation plates.
First, hand sanitizers. One with alcohol as the active ingredient, versus another that was alcohol-free. The key with hand sanitizers is to use at least a half a teaspoon or enough that it takes 15 to 20 seconds before it's dry.
Next, we tried out some soaps. A recent British study showed using soap instead of water alone killed three times as many germs. We pitted regular bar soap against antibacterial bar soap, and regular liquid soap against antibacterial liquid soap.
Each time we washed, we counted out the full 20 seconds the Centers for Disease Control and Prevention recommends -- except once, when we tried another popular timing technique: singing. We sang our ABCs while we scrubbed, which experts say ensures you wash for at least 20 seconds.
E. coli. Wash. Rinse. Dry. Swab. We repeated the process again and again until our hands were chafed. Research shows that most people only dash their hands underwater for about five seconds, if they wash at all.
When she kept track, graduate student Caroline Rocourt was surprised at how long 20 seconds is.
"It's kind of hard to admit," Rocourt said. Wenting Ju, another grad student, said he'd like change his ways -- and at least wash for 10 seconds.
We came back to the University of Maryland three days later, after our samples had incubated.
We looked for white dots where E. coli colonies had grown on the incubation plates. The fewer the better. The first thing we noticed is that alcohol-based hand sanitizer clearly works the best.
In fact, the CDC says you should use a hand sanitizer containing at least 60 percent alcohol.
As for soap, the antibacterial soap worked only slightly better than the regular soap.
The Food and Drug Administration recommends using only regular soap because of worries that germs will develop resistance, and people will develop laziness from high-tech soap.
"Based on the results that we got, it's really not necessary to use antimicrobials in the products. You can see some difference, but it's really not significant," Meng said. The difference between the amount of E. coli left by regular liquid soap and antibacterial liquid soap was even smaller almost undetectable.
The bottom line on hand washing: Technique is more important than technology.
The E. coli we used for our experiment was a harmless strain, not the deadly E. coli 0-157 bacteria. Swine flu is a virus, but the advice is the same: Alcohol kills viruses and soap -- any soap -- used well, washes them off.
Experts say washing with soap and water is first choice, especially if you have visible dirt on your hands. Sanitizer can't cut through that grime. Hand sanitizer is great for when you can't get to soap and water, and it's actually more effective at eliminating germs because it kills them rather than just removing them.
You should supervise young children when they use alcohol-based hand sanitizer, but poison control centers tell us it tastes so terrible that kids don't usually eat much and don't suffer any ill effects.