Kids who suck their thumbs and bite their nails have ‘fewer allergies’ later in life: study

A kindergartener holds her mom's hand while going to school. Anne Christine / Getty Images

While thumb sucking and nail biting may seem like annoying habits your kids won’t give up, new research suggests these vices could make your little ones less likely to end up with allergies.

Scientists out of New Zealand say that kids who are exposed to germs from sucking their thumbs or biting their nails could be strengthening their immune functions, leaving them less vulnerable to developing allergies.

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

The study was carried out by Hancox’s team at the University of Otago. There, scientists followed the health trajectories of 1,037 kids born in Dunedin, New Zealand, in 1972. They were checked in on several times until they were 32.

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In the study, parents identified their kids as thumb suckers or nail biters at ages five, seven, nine and 11.

READ MORE: Want to avoid allergies in your kids? Try turning off the dishwasher

After that, skin prick tests were carried out at ages 13 and 32 to see if kids had developed any common allergies.

When the kids reached age 13, the scientists saw a disparity between the kids: only 38 per cent of kids who put their fingers to their mouths developed allergies compared to 49 per cent who didn’t.

Only 31 per cent of kids who bit their nails and sucked their thumbs developed allergies, too.

The link existed well into adulthood. Hancox said he adjusted for sex, parental history of allergies, ownership of pets and parental smoking.

But don’t coerce your kids into picking up these habits, the scientists say.

Their findings aren’t enough to point to a “true health benefit,” they warn.

This isn’t the first time scientists have zeroed in on the “hygiene hypothesis” – which points to city kids growing up in a squeaky clean environment to their health’s detriment.

READ MORE: Food allergies nearly twice as common among well-educated, study suggests

Last year, Swedish doctors out of the University of Gothenburg suggested that parents are better off hand washing their dirty plates instead of turning to the dishwasher.

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They said that kids “need” exposure to germs, bacteria and dirt so their immune systems get a hearty workout.

In the Swedish study, eczema, hay fever and asthma were considered. Kids who grew up with a sink of dirty dishes their family tended to, had half the allergies of their peers whose households relied on the dishwasher.

If kids were eating farm-grown produce or fermented foods, they fared even better in staving off allergies. Other research has tied pets and living in rural areas as beneficial to kids’ immune systems.

READ MORE: Did dated recommendations contribute to spike of food allergies in kids?

Hancox’s latest findings were published Monday in the journal Pediatrics. Read the study here.


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