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.