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Thumb-sucking, nail-biting linked to lower risk for atopic sensitization
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Children who sucked their thumbs or bit their nails when they were aged 5 to 11 years were less likely to develop atopic sensitization at age 13, an effect that persisted into adulthood, according to study findings.
Malcolm R. Sears
“Thumb-sucking and nail-biting are common oral habits among children, although the reported prevalence varies widely, from less than1% to 25%,” researcher Malcolm R. Sears, MD, of McMaster University’s Michael G. DeGroote School of Medicine, and colleagues wrote. “These habits have the potential to increase the exposure to environmental microorganisms, and have been associated with the oral carriage of Enterobacteriaceae, such as Escherichia coli and intestinal parasite infections.”
To determine whether children who exhibit these behaviors had a reduced risk for developing atopy, asthma, and hay fever, Sears and colleagues analyzed participants in the Dunedin Multidisciplinary Health and Development Study. The prospective longitudinal population-based birth cohort study followed more than 1,000 children from New Zealand to age 38 years.
Parents were instructed to report their children’s thumb-sucking and nail-biting habits at ages 5, 7, 9, and 11 years. By using logistic regression — adjusted for sex and other potentially contributing influences, such as parental atopy, breast-feeding, pet ownership, socioeconomic status, and parental smoking — the researchers assessed associations between thumb-sucking and nail-biting during childhood.
Sears and colleagues wrote that 31% of children who were frequent thumb-suckers or nail-biters at one or more of these ages had a reduced risk for atopic sensitization at age 13 years (OR = 0.67, 95% CI, 0.48–0.92) and at age 32 (OR = 0.61, 95% CI, 0.46–0.81). The researchers also found those who had both habits were at even lower risk for atopic sensitization. No reported associations were observed for nail-biting, thumb-sucking, and asthma or hay fever at age 13 or age 32.
“Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies,” Sears said in a press release. “While we don’t recommend that these habits should be encouraged, there does appear to be a positive side to these habits.” – by Savannah Demko
Disclosure: The researchers report no relevant financial disclosures.
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