Can nail-biting and thumb-sucking be a healthy habit?

Good news for parents who have struggled to get their kids to take their fingers out of their mouths: nail biting and thumb-sucking might have health benefits.

Those habits, scientists found in a recent study, were linked to less risk of allergies to a host of things — including dust mites, animals, and common molds.

The findings support what's known as the "hygiene hypothesis," or the idea that a too-clean environment is to blame for the rise of children's allergies. According to the hypothesis, children who are exposed to some germs early in life develop immune systems that can tolerate contact with different allergens.

Other research has shown that children who own pets, attend day care, live on a farm or have many siblings tend to be less prone to allergies. One study found that babies whose mothers cleaned their pacifiers by sucking the object clean were less at risk for asthma.

For the nail biting and thumb-sucking study, about 1,000 children from New Zealand participated and were assessed periodically, starting at age 3.

A skin-prick test was used to see if there was an allergic reaction to common allergens. The nail biters and thumb-suckers were significantly less likely to test positive for many allergies when they were 13 and 32 years old. But their oral habits didn't have any bearing on their risk of having asthma or hay fever, the New Zealand researchers noted.

Of course, there are other concerns around nail-biting and thumb-sucking, among them: gum injury and social stigma. Acknowledging these concerns, the authors said that they are not making any recommendations.

"Although we do not suggest that children should be encouraged to take up these oral habits," they wrote, "the findings suggest that thumb-sucking and nail-biting reduce the risk for developing sensitization to common (allergens)."

Their findings appear in a recent issue of the journal Pediatrics.

"To Your Health" offers quick doses of health news several times a week.

Allie Shah • 612-673-4488

@allieshah