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Thumb-Sucking and Nail-Biting May Lead to Lower Risk of Allergies

ByJulia DavisNOVA NextNOVA Next

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For years, parents have been hounding their children to get their fingers out of their mouths and stop that thumb-sucking or nail-biting (or in some cases, both) that’s so often seen in young children. Many parents harbor the concern that so much finger-to-mouth time may affect the teeth or the development of speech.

But it turns out there may be a hidden advantage to all those years of wrinkly thumbs and super short nails.

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Thumb Sucking
Babies begin sucking their thumb at a young age, a behavior that sometimes persists after the child has stopped breastfeeding.

In a study published Monday in the journal Pediatrics , children who were described by their parents as thumb-suckers or nail-biters were less likely to test positive for certain allergens later in life.

The study examined 1,037 children in New Zealand, who were tested periodically as they grew up.

Here’s Perri Klass, reporting for The New York Times :

In the study, parents were asked about their children’s nail-biting and thumb-sucking habits when the children were 5, 7, 9 and 11 years old. Skin testing for allergic sensitization to a range of common allergens including dust mites, grass, cats, dogs, horses and common molds was done when the children were 13 years old, and then later when they were 32. Thirty-one percent of the children were described as “frequent” nail biters or thumb suckers (or both) at one or more of those ages.

The study found that children who frequently sucked a thumb or bit their nails were significantly less likely to have positive allergic skin tests both at 13 and again at 32. Children with both habits were even less likely to have a positive skin test than those with only one of the habits.

Even when factors that are usually associated with allergy risk, such as pets, parents with allergies, breastfeeding, and socioeconomic status, were taken into account, the study’s results remained true.

The study is one of many to look into the controversial hygiene hypothesis. Formulated in 1989, the hypothesis suggests that there may be a link between diseases that accelerate the immune system, like eczema, asthma, and allergy, and a lack of exposure to various microbes early in life. When children are frequently putting their hands in their mouth, as they do if they suck their thumb or bit their nails, they are exposing themselves to an ecosystem of microbes from the world around them.

In turns out, according to the results of this study, that some exposure may actually help train a child’s immune system to fight off disease instead of eliciting an allergic response. However, the study found that there was no decrease in cases of asthma or hay fever amongst the children studied.

Although thumb-sucking and nail-biting can be issues for children, often they will end up stopping on their own, developmental pediatrician Lynn Davidson told The New York Times . If a child is getting older and still holding on to the habit, Davidson suggests analyzing when and why they resort to sucking their thumb or biting their nails, and using behavioral techniques like squeezing a foam ball to slowly change the habit.

But this study suggests that at a young age, having a certain affinity for your thumb and fingers is not necessarily a bad thing. In fact, it may just be good for you.

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