Kids health

Study says thumb-sucking and nail-biting can benefit kids

They're still not great habits, but it turns out they can protect kids from allergies.

By Jaclyn Law

660x660 Photo: Colourbox

If the sight of your kid sucking her thumb or biting his nails makes you cringe, you can at least rest assured that there may be an upside to these "bad" habits. Turns out they may actually protect kids from developing allergies later in life.

A study published in the journal Pediatrics has found that children who suck their thumbs or bite their nails are less likely to develop sensitivities to common allergens such as grass, dust mites, airborne fungi, cats, dogs and horses. Kids who are thumb-suckers and nail-biters are even less prone to these allergies. (The study didn’t find a similar connection between oral habits and asthma or hay fever.)

The long-running study was completed by researchers at New Zealand’s Dunedin School of Medicine, with assistance from Malcolm Sears at McMaster University's Michael G. DeGroote School of Medicine.

To test the theory that early exposure to germs and dirt reduces the risk of atopic sensitization (development of allergic reactions), the study followed more than 1,000 children, born in 1972-1973, into adulthood. About 30 percent were frequent thumb-suckers or nail-biters. By age 13, 45 percent of all participants experienced allergic reactions, but only 40 percent of those with one oral habit, and 31 percent of those with both habits. This trend continued as the kids grew up, and factors like exposure to house dust mites, pet cats and dogs, and smokers in the household made no difference.

While oral habits shouldn’t be encouraged or even ignored—thumb-sucking can eventually cause dental problems, and nail-biting can cause infections and other issues—it’s somewhat reassuring that they’re doing some good.