It's healthy for kids to get dirty

Researchers at UC San Diego say that being covered in Staphylococci bacteria "blocked a vital step in a cascade of events that led to inflammation," after an injury.

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.

Head of the research Professor Richard Gallo said: "The exciting implication of the work is that it provides a molecular basis to understand the hygiene hypothesis and has uncovered elements of the wound repair response that were previously unknown.

Dirt can be good for children, say scientists