Bacteria live in the soil and on plants, animals and humans. The prolific numbers of bacteria in the world, with an estimated 10,000 species in a single gram of soil and nearly 500 species in human mouth, mean that bacteria outnumber humans. They are tiny. In fact, they are so small they require a high-powered microscope to be seen.
It is important to understand bacteria and the roles they play, as they are important in the ongoing cycle of life and death. They exist in the air inhaled, on the surface of skin and in mucus membranes. Many antibacterial products have been developed, and these can be helpful, when in the presence individuals who are sick. An oveuse of antibacterial products, however, may be harmful.
Bacteria line the surface of mucus in the respiratory tract, the digestive system and the urinary system. Their mere presence inhibits the colonization of "bad" bacteria, or those that would be disease producing. The wide range of normal flora actually create a barrier to disease-producing bacteria, so overuse of antibacterial products can kill these good bacteria.