- touching surfaces, people, pets, etc. and putting our fingers near our mouths,
- eating live fermented food, or semi-clean vegetables,
- not cooking/killing/sanitizing all of the bacteria around us,
- eating probiotics and transferring some of their genes to our gut flora.
- using inappropriate hygiene that kills the bacteria we need for health,
- taking antibiotics that kill gut flora and compromise our immune system,
- trying to eat a wide variety of foods, which is counterproductive and only permits a few varieties of bacteria to survive.