"Good hand washing can block the transmission of most common diseases," says Charles Shubin, MD, medical director of the Children's Health Center at Mercy Family Care, in Baltimore. Indeed, a study conducted by the CDC in the poorest neighborhoods of Karachi, Pakistan, found that frequent hand washing cut the rates of pneumonia and diarrhea by half.
It's when they touch contaminated surfaces, such as a friend's hand or a toy, and then put their fingers in their mouth or nose or rub their eyes that kids typically pick up germs that cause respiratory infections and diarrhea. Although most health experts recommend scrubbing your hands with soap in warm water for at least 20 seconds -- the time it takes for two rounds of the "Happy Birthday" song -- research shows that even a 10-second wash removes about 90 percent of germs. This doesn't kill illness-causing bacteria and viruses, but it lifts them off skin and cuts infection risk. When there's no water around, use an alcohol-based hand sanitizer.
Also make sure your entire family is current with vaccinations, including an annual flu shot for children older than 6 months. "The idea is to have a cocoon of protection around them," Dr. Iskander says.