Do you actually have to wash your hands for 20 seconds?

As flu season surges on, there's an easy way to reduce your risk of getting sick: Wash your hands properly.

It may seem like common sense, but handwashing is one of the most important of ways of preventing the spread of infection, says Dr. Eric Ascher, a family medicine physician at Northwell’s Lenox Hill Hospital.

"Over 80% of infections are transmitted by hands which carry germs from these surfaces and transfer them into the eyes, nose or mouth," he says. "It is especially important to wash your hands before and after touching shared surfaces, and before eating or touching your face."

His rule of thumb? "Once you enter your home, you should wash your hands."

Here are other common questions about proper hand washing, answered.