THE CASE FOR KIDS GETTING DIRTY

BBC - Children should be allowed to get dirty, according to scientists who have found being too clean can impair the skin's ability to heal.

Normal bacteria living on the skin trigger a pathway that helps prevent inflammation when we get hurt, the US team discovered.

The bugs dampen down overactive immune responses that can cause cuts and grazes to swell, they say.

Their work is published in the online edition of Nature Medicine.

Experts said the findings provided an explanation for the "hygiene hypothesis", which holds that exposure to germs during early childhood primes the body against allergies.

Many believe our obsession with cleanliness is to blame for the recent boom in allergies in developed countries.

Researchers from the School of Medicine at University of California, San Diego, found a common bacterial species, known as Staphylococci, blocked a vital step in a cascade of events that led to inflammation. Rates of allergy have tripled in the UK in the last decade. One in three people now has some kind of allergy.

By studying mice and human cells, they found the harmless bacteria did this by making a molecule called lipoteichoic acid or LTA, which acted on keratinocytes - the main cell types found in the outer layer of the skin.

The LTA keeps the keratinocytes in check, stopping them from mounting an aggressive inflammatory response.

PS: Your editor, who has lived an exceptionally healthy life, credits in part the fact that the home in which he lived his first ten years was built on the former site of a trash dump. I was into my teens before I realized that not all dirt had broken glass and tin in it. I mentioned this recently to my urologist, who agreed. He had grown up on a site used to dump WW I ammunition. - Sam