Could your kids’ thumb-sucking and nail-biting be a good thing?

Thumb-sucking and nail-biting are often considered bad habits and can drive some parents crazy. But a new study found a surprising benefit for these finger-in-mouth kids, namely that they are less likely to develop allergic sensitivities.

The longitudinal study published in the journal Pediatrics followed over a thousand children born in New Zealand in the 70s and assessed them as they grew into adulthood. Of the children studied, 31 percent were found to be frequent thumb-suckers and nail-biters. For the purpose of the study, atopic sensitization – a predisposition toward developing allergic reactions – was measured by a skin prick test as a child (at age 13) and as an adult (age 32).

The researchers found that of all the children at age thirteen who neither sucked their thumbs nor bit their nails, 49 percent had risk of atopic sensitization. But kids with one habit (either thumb-sucking or nail-biting) were less likely to be atopic; their risk was only 40 percent. Finally, kids that were both thumb-suckers and nail-biters had the lowest risk at 31 percent.

The same trend continued when tested into adulthood.

“The findings support the ‘hygiene hypothesis,’ which suggests that being exposed to microbes as a child reduces your risk of developing allergies,” said study lead author Bob Hancox in a statement.

Dr. Javeed Akhter, an allergy and immunology specialist at Advocate Children’s Hospital at Christ Medical Center in Oak Lawn, Ill., agrees that the findings are just “another bit of data that supports the ‘hygiene hypothesis’ in a large study where children were followed through adulthood.”

But Dr. Akhter cautions that while lower rates of sensitization were revealed, it is worth noting that sensitization and clinical allergy are not the same thing. “The risk for diagnosed asthma and allergic rhinitis [hay fever] was the same for both groups,” he notes.