A new study from the University of Otago, New Zealand, found kids who exhibit thumb-sucking or nail-biting behaviours could be less at risk of developing allergies later in life.
The findings are just one result from the Dunedin Multidisciplinary Study, a long-running data collection exercise that has followed the lives of 1,037 participants born in 1972 and 1973.
The paper, which appears in the August issue of the US-based journal, Pediatrics, suggests childhood exposure to microbial organisms via thumb-sucking and nail-biting could reduce the risk of developing allergies.
Parents of the participating children were asked to report their thumb-sucking and nail-biting behaviour at ages 5, 7, 9, and 11 years of age. Each of the participants was then checked at page 13 and 32 years old for ‘atopic sensitisation’, which is a positive result on a skin prick test to at least one common allergen.
Results show that the prevalence of sensitisation was lower among children who had sucked their thumbs or bit their nails by 38 percent, compared to those who didn’t at 49 percent. Children who were reported to both suck their thumbs and bite nails had an even lower risk of allergy at 31 percent.
Lead author of the study, Professor Bob Hancox said the exposure to microbes as a result of these behaviours may alter immune functions, resulting in the children becoming less prone to allergy.
“The findings support the “hygiene hypothesis”, which suggests that being exposed to microbes as a child reduces your risk of developing allergies,” he says.
At the same time, Professor Hancox and the other co-authors of the report stress that their findings aren’t grounds for encouraging children to acquire these habits, as it’s not clear as to the net health benefits of such behaviour.
Stephanie Lynch, a medical student who co-authored the study as a summer project, says “although thumb-suckers and nail-biters had fewer allergies on skin testing, we found no difference in their risk for developing allergic diseases such as asthma or hay fever”.