Many books on parenting and child psychology include extensive discussions of the perils of thumb sucking and nail biting, and offer an array of (sometimes bizarre) suggestions to “conquer” these behaviors. Among the many ills attributed to these behaviors are a perceived risk of developing addictive disorders, malformation of developing teeth, speech abnormalities and infections.
A recent prospective study of over 1,000 children in New Zealand reports that children that are frequent thumb-suckers or nail-biters at age one or older are significantly less likely to have allergies at age 13 and also at age 32. Indeed, the researchers found that children that suck their thumb AND bite their nails have the lowest likelihood of developing allergies later in life.
The “benefit” of sticking dirty fingers in our mouth may have to do with the hygiene hypothesis, which postulates that lack of exposure to infectious agents in early childhood suppresses the natural development of the immune system, resulting in increased susceptibility to allergens.