The skin is underappreciated as the most important organ of the body because it protects humans from the environment. The skin not only protects humans from physical insults, from a splinter to harmful ultraviolet rays from the sun but also dangerous microbes, especially bacteria. The skin provides a hospitable environment for friendly bacteria that live on our skin thus preventing dangerous bacteria from taking up residence on the skin and causing harm.
Once the skin surface is broken, whether from a scrape, scratch, burn or surgical wound, dangerous bacteria can invade leading to infections in the skin. On injury, the skin in fact produces its own natural antibiotics called antimicrobial peptides or proteins. The first one discovered over 20 years ago is named human β-defensin 2 and has broad spectrum antibiotic activity meaning it kills many different types of bacteria. More recently another antibiotic manufactured in the skin, cathelicidin LL-37 was discovered to not only directly kill invading bacteria but it also regulates the inflammatory response to an injury by attracting our own immune cell that help fight infections in the wound. Cathelicidin LL-37 binds to the surface molecule, Lipopolysaccharides that is found on many bacteria. On binding the cathelicidin LL-37 destroys the bacteria. In addition, this amazing chemical promotes new surface skin cells to cover the wound and it also promotes wound closure.
Small wounds can prove deadly such as the superficial skin infection called cellulitis which if left untreated can lead to a dangerous blood infection called sepsis. Deeper more dangerous infections such as necrotizing fasciitis, commonly referred to as the flesh-eating disease can start from a minor cut and quickly cause death if surgery is not performed in a timely manner.