New study: Thumb-sucking and nail-biting might lead to less allergies later on

A new study, published this month in the American Academy of Pediatrics’ “Pediatrics” gave us more evidence that the “hygiene hypothesis” might have some truth to it. The hygiene hypothesis says that exposing kids to dirt and germs is a good thing and that children in the Western world could be growing up in t00-clean environments. This study came out of New Zealand.

Thumb-sucking might actually help kids build up immunity to some allergens. Ralph Barrera Austin American-Statesman
Thumb-sucking might actually help kids build up immunity to some allergens.
Ralph Barrera Austin American-Statesman

This study looked at 1,037 participants and assessed them when they were 3, 5, 7, 9, 11, 13, 15, 18, 21, 26, 32 and 38 years old. The participants were identified as either thumb-suckers or nail-biters if they continued to do it between ages 5 and 11. The study tested participants for allergy sensitivities, asthma and hay fever. Researchers found that those thumb-sucking or nail-biting children had a lower risk of allergies at age 13 as noted by a skin prick test, but nail-biting and/or thumb-sucking didn’t really help with asthma or hay fever. The thumb-suckers and nail-biters also still had a lower risk for allergy sensitivities at age 32.

At age 13, 38 percent of the the

thumb-suckers and/or nail biters had an allergy sensitivity compared with 49 percent of their non-thumb-sucking, nail-biting peers. 40 percent of children who had only one “bad habit” had an allergy, but 31 percent of those that had both habits had an allergy.

For parents, does this mean they should go out and encourage their children to suck their thumbs or bite their nails?

No, says Dr. Mai Duong a pediatrician and co-chief of pediatrics at Austin Regional Clinic. With thumb-sucking and nail-biting, parents do have to worry about tissue and skin infections, Duong says. “The human mouth is never clean,” she says.

While this study  might give parents of thumb-suckers and nail-biters some reassurance, not enough is known about the hygiene hypothesis. “We don’t know enough about what exposure is good,” she says. And, of course, there are some germs you don’t want any exposure to at all.

Duong doesn’t see the American Academy of Pediatrics and pediatricians changing their recommendations on the level of cleanliness you should give your child. Even with this study and previous studies, Duong recommends parents take precautions especially for newborns. That means sterilizing pacifiers and bottles. It means washing your hands before and after a diaper change. And it means washing around a baby’s nose and mouth, especially those first three months.



Author: Nicole Villalpando

Nicole Villalpando writes about families in the Raising Austin blog and the Raising Austin column on Saturdays. She also offers a weekly and monthly family calendar at She tweets at @raisingaustin.

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