Given how much money we spend on wrinkle remedies, bronzing creams and mud facials, you'd think our skin is mere decoration. But disturbing as this may seem to you readers with disinfecting wipes in your pockets, the normal human epidermis doubles as a complex ecosystem every bit as vibrant as the Amazon rainforest or the African Serengeti.
Our external surface area, which ranges from an average of 1.6 square meters in adult women to 1.9 square meters in men, is populated by a vast number of other life forms [source: Medterms.com]. Just how vast? Your hide is home to approximately 1 trillion bacteria, which is about 150 times the entire human population of our planet [source: Todar]. That population includes close to 500 different bacterial species, including 44 that live in the neighborhood that covers your forearm and another 19 who own real estate behind your ears [source: Science Daily, Science Daily]. That's not necessarily a bad thing, either. Some of the bacteria on your skin perform beneficial functions, like preventing excessive inflammation after injuries to the skin [source: Warner].
Additionally, you may have scores of other tiny tenants, from the mites that live in your eyebrows, to fungi and small insects. Some are harmless, while others cause unpleasant but minor skin ailments, like acne or jock itch. But more than a few can cause potentially serious illnesses, such as antibiotic-resistant infections or Lyme disease. So, we need to be careful what creatures we host.
Here's a look at 10 life forms crawling around on our skin.