A new study published in the journal Pediatrics reports that children who bite their nails or suck their thumbs may be at a lower risk for developing allergies. The reason for this is thought to be that these “dirty habits” are actually leading to early exposure to germs, which strengthens the immune system.
The study, from the New Zealand’s University of Otago, along with Canada’s McMaster University, acknowledges that the habits are bad for teeth, and definitely does not encourage them. However, the researchers found that thumb-sucking and nail-biting lead to a natural early exposure to all kinds of allergens, including dust, animal hair and grass. The immune system is thus given a chance to develop natural defenses.
The study followed 1,000 New Zealand children at ages 5, 7, 9 and 11. When tested at ages 13 and 32 with skin prick allergy tests, 49 percent of the children who had neither habit showed atopic sensitisation in the skin-prick test. However, this dropped to 38 percent in those who did suck their thumbs or bite their nails. Those children who had both habits were at an even lower risk of allergies, at only 31 percent. The results remained consistent with the second test at age 32, despite outside factors such as parental history, pet ownership and gender.
Orthodontists are not happy with the thumb sucking. The longer a child sucks their thumb, beyond 2 or 3 years of age, the higher the risk of developing oral malformations, such as an anterior open bite where the upper teeth are not in contact with the bottom teeth when the mouth is closed. However, pacifiers are an even bigger concern, since the child has to suck harder on it to keep the device in their mouth, which can be bad for the palette.
Stephanie Lynch, a medical student who is part of the current study, said she hopes the results encourage people to think twice about letting their kids get a little dirty. “The study kind of shows that maybe being too clean isn’t that good for you and parents shouldn’t be afraid to let their kids get dirty or let them have dirt under their nails.”