Your toddler eats dirt. Remember not all germs are bad. "Don't worry about a cookie falling on the floor or eating a little dirt, but by the same token, don't deliberately expose kids to sick people," said science writer Jessica Snyder Sachs, author of "Good Germs, Bad Germs" (Hill and Wang, $14), which examines how public sanitation and antibiotic drugs have disrupted the balance we're supposed to have with our resident micro-organisms. THE VERDICT: Minimal risk.