You touch the door on the way out of a public bathroom. More than half the patrons wash their hands, said University of Arizona microbiologist Charles Gerba, who has studied everything from urine levels in public pools to germs in airline bathrooms. But if you're still worried, wash your hands and then use a hand towel to open the door, said Harley Rotbart, a pediatric infectious disease specialist and author of "Germ Proof Your Kids" (American Society for Microbiology, $26.95). Wiping your hands on a towel further reduces the germ load, so avoid the hot air dryer. Skip the anti-bacterial soap too. These ubiquitous products, which usually contain the chemical triclosan, don't prevent colds or flu, which are caused by viruses, not bacteria. And they haven't been shown to reduce infection rates any better than soap and water. THE VERDICT: Minimal risk.