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Being too clean may be bad for you

New research suggests being too clean may impede the skin's natural ability to heal itself.

American scientists say bacteria on the skin's surface plays an active role in fighting inflammation.

Professor Richard Gallo, who spearheaded the research at the University of California in San Diego, said the bugs dampen down over-active immune responses which can lead to rashes or cause cuts and bruises to become swollen and painful.

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 hay fever and eczema are less common among children from large families with a greater risk of spreading infection. It was also used to explain the high rates of allergic diseases in "cleaner" industrialised countries.

Skin bacteria include certain staphylococcal species that can promote inflammation when introduced 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 human cell cultures show they actually reduce skin inflammation.

The research appears online in the journal Nature Medicine.

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Nature Medicine