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Nail-biting and thumb-sucking are apparently more than yucky habits growing up; turns out, children who take part in either have fewer allergies as they age.
The study — published in the journal Pediatrics — further lends credence to the hygiene hypothesis: early-life exposure to some microbial organisms strengthens one's immune system. The news is good; since children rarely discriminate against sticking their fingers in the mouth, even if you try to deter them by coating their nails with Paprika (Sorry, mom!).
Researchers assessed roughly 1,000 participants in New Zealand, between ages five and 32 years old. Thumb-sucking and nail-biting were recorded at ages five, seven, nine and 11, and the presence of allergies were tested at ages 13 and 32. Roughly one-third of the participants were considered nail-biters and/or thumb-suckers and researchers found those participants were significantly less likely to have allergies at age 13. Their odds of developing pet allergies was also significantly lower than those participants who did not suck on thumbs or bite nails.
The study should also make parents feel less guilty about not keeping up with housework — since children are less likely to be exposed to healthy germs in a squeaky clean household. Experts say that allowing germs to flourish here and there could help keep children from developing allergies, as they may develop more resistance toward pet dander and pollen. So how can a dirty home keep kids healthy? One hypothesis is that exposure to pathogens lets the immune system adapt as it learns to tell the difference between harmless and harmful irritants.
