According to new research by the University of Otago in Dunedin, New Zealand, children who bite their nails and suck their thumbs may be less likely to develop allergies as they get older. The study has been published in the journal Pediatrics.
The explanation for this beneficial effect of a bad habit is that children are exposed to more microbes, which in turn alters their immune system and makes them less likely to develop allergies.
To reach this conclusion, the experts used data from the Dunedin multidisciplinary study that followed 1,037 participants from birth to adulthood for no less than 40 years. The volunteers underwent skin prick tests at 13 and 32 years of age where a positive result indicates that that person is at higher risk of developing an allergy to the source of the allergen in particular, such as cats, house dust , plants…
Results at age 13 showed that only 38% of participants who used to suck their thumb or bite their nails tested positive for at least one allergen, compared with 49% who did not have any of these habits. If they had both behaviors, the percentage decreased to 31%.
The results, when the participants were 32 years old , were still as striking even taking into account factors such as gender, a history of allergy in the parents, having a pet in childhood, the smoking habit of the parents and breastfeeding .
The study thus suggests that exposing a child to microbes – by thumb sucking or nail biting – reduces their risk of developing allergies. However, “even if the results support this hypothesis, children should not be encouraged to do so,” explains Bob Hancox, leader of the work.
