For parents too stretched to make sure their offspring are perfectly turned out at all times, it may just be the scientific cover they’ve been waiting for.

They will now be able to answer the disapproving tuts of their more fastidious friends by pointing to research which gives biological backing to the old adage that the more germs a child is exposed to during early childhood, the better their immune system in later life

Researchers from the School of Medicine at the University of California found that being too clean could impair the skin’s ability to heal. The San Diego-based team discovered that normal bacteria that live on the skin trigger a pathway that helps prevent inflammation when we get hurt.

These bugs dampen down overactive immune responses which can cause cuts and grazes to swell, or lead to rashes, according to research published in the online edition of Nature Medicine.

“These germs are actually good for us,” said Professor Richard Gallo, who led the research. Common bacterial species, known as staphylococci, which can cause inflammation when under the skin, are “good bacteria” when on the surface, where they can reduce inflammation.

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