Think a good antibacterial hand soap is keeping your skin relatively microbe and bacteria free? You might want to think again.

Scientists and germophobes alike have long known that human skin—from head to toe—is literally crawling with bacteria and microbes. And a new study, published today in Science shows that skin is host to many, many more of the tiny organisms than previously thought. 

Researchers at the National Institutes of Health's (NIH) new Human Microbiome Project sequenced genes from skin samples from volunteers and found bacteria that hailed from 19 different phyla, 205 genera and possessed more than 112,000 individual gene sequences. (Previous studies of skin cultures supposed that just one type of bacteria, Staphylococcus—a virulent strain of which is responsible for staph infections—was the main resident of human skin.) But no need to overdo it on the antibacterials; most of the tiny organisms aren't doing any harm.

All of these samples were collected from 20 different disease-prone spots on the bodies of 10 healthy volunteers—from forehead to heel, with stops such as the buttock and inner elbow along the way.

After completing this initial survey, researchers aim to establish a bacterial baseline so as to better treat skin diseases, such as acne or eczema, where bacterial populations might be out of whack.

"The skin is…an ecosystem, harboring microbial communities that live in a range of physiologically and topographically distinct niches," the study authors write. "For example, hairy, moist underarms lie a short distance from smooth, dry forearms, but these two niches are as ecologically dissimilar as rainforests are to deserts."

Can you guess the location with the most types of bacteria? No, it's not the "rainforest" or below the belt. Try the forearm, which boasts an average of 44 different species.

Image of bacteria cultured from human skin courtesy of Julie Sergre