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| Good news about bad habits |
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Could there really be an upside to nail-biting and thumb-sucking? A new study out of Otago University in New Zealand says 'Yes' and has shown that children who regularly engage in these activities may be less likely to develop allergies in later life.
The study suggests that childhood exposure to microbial organisms through thumb-sucking and nail-biting reduces the risk of developing allergies.
The finding emerges from the long-running Dunedin Multidisciplinary Study, which has followed the progress of 1,037 participants born in 1972-1973 into adulthood.
Study lead Professor Bob Hancox says that this exposure may alter immune function so that children with these habits become less prone to developing allergy.
The study, which appears in the August issue of the US journal Pediatrics, asked parents of the study members to report on their children's thumb-sucking and nail-biting habits when their children were ages 5, 7, 9, and 11 years old.
The members were checked at ages 13 and 32 years old for atopic sensitisation, which is a positive skin prick test to at least one common allergen.
At age 13, the prevalence of sensitisation was lower among children who had sucked their thumbs or bit their nails (38 per cent) compared with those who did not (49 per cent).
Children who both bit their nails and sucked their thumbs had an even lower risk of allergy (31 per cent), Professor Hancox says.
The associations were still present at age 32 years and persisted even with adjustments for confounding factors such as sex, parental history of allergies, pet ownership, breast-feeding and parental smoking.
"The findings support the "hygiene hypothesis", which suggests that being exposed to microbes as a child reduces your risk of developing allergies," he says.
Despite these findings, Professor Hancox and his co-authors do not suggest that children should be encouraged to take up these habits, because it is unclear if there is a true health benefit.
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