Thumb sucking and nail biting protects against allergies

Thumb sucking and nail biting protects against allergies, researchers say. Research scientists from New Zealand Otago University published data from a completed longitudinal study in the American journal Paediatrics The researchers examined 1,000 children aged five to eleven years. The Otago University study found children who sucked their thumb or bit their nails were much less likely to develop allergies in later life.

The result was surprising: They tested whether the children who were reported to bite their nails or suck their thumbs when they were between the ages of 5 and 11, were at greater risk of developing allergies by the age of 13. The group were tested for skin allergies at the age of 13 and again at 32 years.

About a third of the group sucked their thumb between the ages of 5 and 11, another third bit their nails and a smaller group did both.

"What we found was that the children who bit their nails or sucked their thumb had about a 30 to 40 percent lower risk of having an allergy at the age of 13, and what's more this persisted right up until the age of 32."

Children in a group who did both had the lowest risk of developing allergies. The result support the "hygiene hypothesis", that earlier contact with dirt and germs reduces the risk of allergies. Study author Malcolm Sears.