They say that being too clean means skin doesn’t heal as well.

The American scientists found that normal bacteria living on the skin helped to prevent inflammation when we get hurt.

Some experts believe that an increase in allergies is down to people being more obsessed with being clean.

A woman from Allergy UK said that one in three people has some kind of allergy now. She added that there was some evidence that being exposed to germs helped stop people becoming allergic but more research was needed to prove it.