Do you wear your shoes in the house or leave them at the door? It's an especially important choice for people with small children who play on the floor.
In some countries and cultures, it's scandalous to walk into a home with shoes on. But in the U.S., most people do.
"I don't really think that much about it," said New Jersey mom Michelle Ciocon.
"Good Morning America" tested the bottoms of eight different people's shoes, as well as two dogs' paws, for bacteria. Ciocon's shoes contained the most bacteria of all — 66 million organisms.
It's no reflection on her; she probably just stepped directly in something.
In a recent study, researchers at the University of Arizona found nine different species of bacteria on people's shoes. These types of bacteria can cause infections in our stomachs, eyes and lungs.
The study also found bacteria live longer on our shoes than in other places. As we walk, we constantly pick up new debris that feeds the growth of more bacteria.
The researchers tested to see if bacteria on shoes would transfer to the tile floors in a house. More than 90 percent of the time it did. Carpeting harbors bacteria even more.
"GMA's" test results were "dirtier than a toilet seat," said Jonathan Sexton, a research assistant at the University of Arizona's College of Public Health. "Toilet seats generally have 1,000 bacteria or less, and these are in the millions so there's a lot more bacteria here."
The results troubled Ciocon.
"I'm concerned," she said. "I'm going to make sure everyone takes their shoes off from now on. As soon as they get to that door, their shoes are going to be off."
Children under age 2 are the most vulnerable to the germs we track into the house, because they play on the floor and put their hands in their mouths an average of 80 times an hour.
"That means that your child can possibly be exposed to every single bacteria that you picked up on your shoe [...] all the bacteria from the park, the store, everywhere you went that day," Sexton said.
Out of "GMA's" 10 tests, nine contained coliform, a type of bacteria that comes mostly from human and animal waste.
Scientists blame the floors of public restrooms and bird and dog droppings. The dogs in "GMA's" test came in fifth and ninth place for dirtiest soles.
But that doesn't mean dogs are cleaner than people. One of the dogs in the test had just been for a walk in the rain, which probably cleaned his paws. Also, paws are much smaller than our shoes, so they carry fewer germs.
The easiest way to ensure that you don't track the germs on your shoe soles into your home is to leave your shoes at the door or carry them to the closet. Then you should wash your hands.
Researchers found washing shoes in the washing machine on the cold cycle, with detergent, killed the bacteria. So for some shoes that might be an option. You can also wipe them with a disinfectant.
While you may be comfortable taking your footwear off before entering your home, you may not know how to ask guests to do so.
Anna Post, author and spokesperson for the Emily Post Institute, which offers advice on manners and etiquette, said when having visitors in your home, removing shoes is something you can ask of a guests. But you have to keep in mind that everyone might not be comfortable with that, she added.