There are over 200 species of microorganisms that exist in the human body and a large part of them are distributed in the gastrointestinal tract. The microorganisms in the gastrointestinal tract include both harmful and beneficial microorganisms.

Microorganisms are distributed everywhere in nature and on both human and animal bodies. Microorganisms include beneficial microorganisms and harmful microorganisms. Of these, only a few species of microorganisms cause disease in humans.

Recent studies in humans and mice show that exposure to environmental microorganisms helps prevent allergies and other inflammatory diseases.