A new study has found that when it comes to killing germs nothing can replace good old-fashioned hand washing.

Hand sanitizer has become more and more popular over the years, but the study shows that if you quickly rub it on your hands it might not be killing cold and flu bugs.

Dr. Matthew Projansky, who works in the ER at Syosset Hospital, says while he is a fan of sanitizers in a pinch the new research shows that the gel would have to sit on your hands for about 4 minutes to actually kill the flu virus.

"Hand sanitizers were never meant to replace hand washing, they were just a supplement," says Projansky. "Because obviously we don't have running water, sinks and soap at every location."

Doctors say the best way to protect yourself is to wash your hands with soap and water, scrub for 20 seconds and dry with a clean towel.