Not much. You stand a much better chance of catching something nasty from the germs living in your kitchen sponges than from anything on your toilet seat, said Dr. Iain Fraser, a pediatric infectious disease specialist at Massachusetts General Hospital.

The image of the toilet seat as a carrier of noxious material “is more an esthetic problem than a health problem,” said Dr. John Bartlett, an infectious disease specialist at the Johns Hopkins University School of Medicine. To be sure, if there is fecal material on the toilet seat and you touch the seat with your hands and then put your hands in your mouth, you may catch an intestinal bug such as salmonella or E. coli. Urine on the seat is probably harmless because urine is usually sterile.

If you have open cuts on your buttocks or thighs, bacteria on the seat could get into your body through the skin, “but this would be a very unusual way of transmission,” said Fraser. In theory, you could catch a cold from a toilet seat, but someone would have had to sneeze on the seat, then you’d have to touch the seat with your hands and then rub your mouth, nose or eyes.

On top of that, toilet seats and other hard surfaces are not good carriers of germs. “That’s not an area where bacteria can live long or well,” said Bartlett. “Skin to skin is a much better transmitter of bugs than windshields or walls or toilet seats.

In other words, to reduce the chances of getting sick, change kitchen sponges often, wash your hands after you touch surfaces that people with colds also touch (phones, doorknobs, subway grab bars), and wash your hands after you use the bathroom for basic hygiene. But don’t worry about catching things from just sitting on the toilet seat.