As someone who sucked her thumb until third grade and has been viciously biting her nails ever since, I am happy to report, as I nip at my cuticles, that there is actually an upside to this neurotic behavior.
A new study published in the journal Pediatrics suggests that children who suck their thumb or bite their nails are less likely to develop allergies. The authors believe it can be explained by the hygiene hypothesis—exposure to some germs strengthens the body's immune system. It's why so many doctors are now encouraging us to "live dirty."
(Note to Mom: See? It's not disgusting—it's smart. Now, leave me alone. Love you.)
For the ongoing study, researchers assessed the nail-biting and thumb-sucking habits of 1,037 children born in New Zealand as they grew up, with the most recent assessment done at age 38. They controlled for pets, parents with allergies, breast-feeding, socioeconomic status, and more.
About a third of the children were frequent thumb-suckers or nail-biters, and these children were significantly less likely to have positive allergic skin tests—in response to a range of common allergens including dust mites and dogs—both at 13 and into adulthood, at 32. And children with both habits were even less likely to have a positive skin test than those with only one of the habits. But there was no significant difference in their likelihood of having asthma or hay fever.
"While we don't recommend that these habits should be encouraged, there does appear to be a positive side to these habits," said co-researcher Professor Malcolm Sears from McMaster University in a press release.
Thumb sucking, particularly in older children, can still be a problem if it interferes with the teeth, affects speech, causes infections on the fingers, or attracts teasing from peers.
And, in my experience, nail-biting has brought me a lot of negative criticism—and not just from my mother. You know what, though? I don't have any known allergies—not that I can prove it has anything to do with my habit. But, yeah, it's probably about time I quit (though this study is not making it any easier).