Germs really are good for us

Staying too clean can harm skin's ability to heal itself, a new study has revealed.

A research team from University of California, San Diego, have discovered that bacteria living on the skin surface prevent excessive inflammation after injury.

"These germs are actually good for us," Dr Richard L. Gallo, professor of medicine and pediatrics, chief of UCSD's Division of Dermatology and the Dermatology section of the Veterans Affairs San Diego Healthcare System.

According to the researchers, lack of early childhood exposure to infectious agents and microorganisms increases an individual's susceptibility to disease by changing how the immune system reacts to such "bacterial invaders."

The hypothesis was first developed to explain why allergies like hay fever and eczema were less common in children from large families, who were presumably exposed to more infectious agents than others.

The team suggests that skin's normal microflora, usually harmless bacteria that live on the skin, includes certain staphylococcal bacterial species that will induce an inflammatory response when they are introduced below the skin's surface, but do not initiate inflammation when present on the epidermis, or outer layer of skin.

During the study, research team led by Yu Ping Lai, Gallo have found a previously unknown mechanism by which a product of staphylococci inhibits skin inflammation.

The inhibition is stimulated by a molecule called staphylococcal lipoteichoic acid (LTA), which acts on keratinocytes - the primary cell types found on the epidermis.

The study is published online in Nature Medicine.