'Dirty' bugs keep skin healthy, say scientists

Published on Sunday 22 November 2009 22:12

BEING too clean may impair the skin's ability to stay healthy and heal itself, new research suggests.

Scientists in the US have discovered that bacteria on the surface of the skin play an active role in combating inflammation.

The bugs dampen down over-active immune responses which can lead to rashes or cause cuts and bruises to become swollen and painful.

"These germs are actually good for us," said Professor Richard Gallo, who led the research team at the University of California in San Diego.

The findings may provide a molecular basis for the "hygiene hypothesis". First proposed in the 1980s, this suggests that early childhood exposure to bugs might "prime" the immune system to prevent allergies. The theory was developed to explain why allergies such as hayfever and eczema are less common among children from large families with a greater risk of spreading infection.

Skin bacteria include staphylococcal species that can promote inflammation when found beneath the skin's surface.

But the same bugs do not trigger inflammation when present on the epidermis, or outer layer, of skin. In fact, the new studies conducted on mice and human cell cultures show they actually reduce skin inflammation.

A previously unknown mechanism was identified by which a product of staphylococci inhibits inflammatory response.

The effect occurs partly because of TLR3, a molecule that can be stimulated to trigger bio- chemical effects.

Prof Gallo said: "To our knowledge, these findings show for the first time that the skin requires TLR3."