Fort Worth, Texas,
15:50 PM

Thumb sucking, nail biting may prevent allergies

New study suggests these 'bad habits' may have benefits

Want to prevent allergies in your child?

A new study suggests you might want to relax about letting your kids suck their thumbs and bite their nails. The study participants compared children with either or both of these “bad” oral habits with those who did not. The subjects underwent skin allergy testing at age 13 and 32. Those who had one of the habits showed decreased skin sensitivity relative to those who did not (38 percent vs 49 percent). Those who both sucked their thumb and bit their nails showed sensitivity rates of 31 percent. An important note is that the study did not find a difference between the two groups for the development of hay fever or asthma.

This falls in line with similar studies that having a dog early or parents who cleaned your pacifier with their mouth also might have the same effect of decreasing sensitivity on allergy testing.

There are many who believe that exposure to more microbial organisms early on might help children develop tolerance and decrease their risk of allergic diseases later on (this is known as the hygiene hypothesis). This study would support that thought and would suggest that our obsession with sterilizing and purifying everything might be creating problems with allergic diseases later in life.

The lack of association with asthma and hay fever suggests that we should use caution as we consider the results of this study. Further research is necessary to determine if the decreased skin sensitivity will actually produce a better clinical outcome with less allergic disease. For now, let’s just let all our parents with thumb suckers and nail biters have a reason to celebrate for a bit.

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Comments 1 - 2 (2)
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Justin Smith, MD
There were about 1000 participants in the study. It's important to note that the study didn't show a decrease in allergic symptoms only the reaction to the skin test. It's an interesting study but not a huge clinical significance at this time. Hopefully we'll learn more about this and be able to use the information more as more studies look at the theory.
M. Kirkland
How large was this study? In my personal experience, I have found the opposite to be true. I have six children, two of whom (now ages 12 & 14) both suck their thumbs and bite their nails. Some of my other children are nail-biters, but these are the only two who have ever sucked their thumbs. Both of these children have severe allergies to foods and pollens. My other four children are allergy-free.