Thumb-sucking is good for your health, new study says

Is nail biting and thumb sucking good for your health?

The supposedly bad habits of thumb-sucking and nail-biting actually have positive health benefits according to a new study which concluded that children who partake in the two oral habits are less likely to develop allergic sensitivities.

“Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies,” says Malcolm Sears of McMaster University’s Michael G. DeGroote School of Medicine, co-author of the study. “While we don’t recommend that these habits should be encouraged, there does appear to be a positive side to these habits.”

The idea that “getting dirty” is good for your health was first proposed in 1989 by epidemiologist David Strachan in an attempt to explain why children from larger families or with older siblings were found to be less likely to develop hay fever. Contrary to accepted wisdom that cleanliness is always the best approach, the hygiene hypothesis maintains that being exposed to a number of infections while still in one’s developmental stages helps to bolster the body’s defenses by introducing a variety of microorganisms and increasing the diversity of a person’s own collection of itty-bitty bugs.

And with the fingernail being a veritable repository of bacteria (much more so than the hands themselves), thumb-sucking and nail-biting are well known to be clear and effective ways of increasing one’s exposure to environmental microorganisms.

Researchers looked to data from the population-based birth cohort study conducted in Dunedin, New Zealand, involving 1037 participants and numerous assessments from birth up to 38 years of age. Parents of the participants were asked about their child’s thumb-sucking and nail-biting status at ages five, seven, nine and eleven years and then skin-prick tests were conducted at 13 and 32 years old to determine atopic sensitization (allergic reaction). The study found that 31 per cent of participants were frequent thumb-suckers and/or nail-biters in childhood and that this group were less likely to show allergic reactions than the other 69 per cent.

In fact, at age 13, 45 per cent of all participants showed atopic sensitization but of those who both sucked their thumbs and bit their nails, only 31 per cent had atopic sensitization, while those with only one of the two habits turned out to have allergies 40 per cent of the time. Just as importantly, the reduced risk of allergic reaction persisted into adulthood.

The study’s authors point out that there is evidence that thumb-sucking and nail-biting are not actually good habits to promote -they have been associated with health problems such as dental malocclusion and gingival injury- but they nonetheless see their results as “contributing to the body of evidence supporting the hygiene hypothesis.”

According to a survey conducted by pharmaceutical company Johnson & Johnson, up to 10-million Canadians suffer from allergy symptoms, with those in Ontario experiencing the highest rates of seasonal allergic reactions and those in Atlantic Canada reporting the lowest rates.

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