Children who bite their nails or suck their thumb cut their risk of developing an allergy as an adult by a fifth

It's a dilemma faced by millions of parents worldwide – how to stop their children sucking their thumb.

But researchers have found that the habit may bring unexpected health benefits – and the same is true for nail biting.

Scientists have discovered that children who sucked their thumbs or bit their nails were more than a fifth less likely to have allergies as adults.