All these hygenic parents who continuously wash and disinfect their children and don’t like them to play in the dirt are doing their progeny a huge disservice.

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.

By studying mice and human cells, researchers discovered that they 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.

Scientists give grubby children a clean bill of health | Life and style | The Guardian.