Have a kiddo who sucks his thumb, or one who bites her nails? Here's why that may not be a bad thing.
young girl sucking her thumb
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Nail-biting and thumb-sucking are typically thought of as nasty habits parents want to break, but a new study published in Pediatrics says these childhood behaviors may not be all bad. Researchers out of New Zealand looked at 1,000 children over three decades and found that kiddos who bite their nails or suck their thumbs are actually less likely to develop allergies, and may develop protective benefits that last into adulthood.

Participating parents reported nail-biting and thumb-sucking habits when their kids were at four different ages: 5, 7, 9, and 11 years old. Researchers also evaluated their allergic status using a skin-prick test at age 13, and then again at 32.

It was determined that 38 percent of kids who were nail-biters or thumb-suckers had at least one allergy, while 49 percent of the non-biters and suckers had at least one allergy. Perhaps most interesting is that researchers found kids who had both "bad" habits were even less likely to have allergies at age 13 (but not at 32) versus those devoted to just one habit.

It's worth noting researchers are not suggesting kids who don't suck their thumbs or bite their nails take up these habits to ward off allergies. "Many parents discourage these habits, and we do not have enough evidence to [advise they] change this," says Dr. Robert Hancox, associate professor of respiratory epidemiology at the University of Otago. "We certainly don't recommend encouraging nail-biting or thumb-sucking, but perhaps if a child has one of these habits and [it] is difficult [for them] to stop, there is some consolation in the knowledge that it might reduce their risk of allergies."

This is just the latest study to support the so-called hygiene hypothesis, which you may be familiar with due to other widely-publicized research that came out in 2013, which found that when moms sucked their babies' pacifiers clean, the babies were less likely to develop allergies. "Although the mechanism and age of exposure [to pathogens] are different, both studies suggest that the immune response and risk of allergies may be influenced by exposure to oral bacteria or other microbes," the researchers wrote in this study.

So basically, attempting to keep our kids "too clean" and germ-free could actually be harming them. Maybe. I'm still insisting my kids wash their hands after they play at the park. But as a mom of a devoted thumb-sucker, I'll admit I was excited to hear there's a silver lining to my daughter's need to have a digit in her mouth morning, noon, and night.

Melissa Willets is a writer/blogger and a mom. Follow her on Twitter (@Spitupnsuburbs), where she chronicles her love of exercising and drinking coffee, but never simultaneously.