Thumb-Sucking, Nail-Biting, and Atopic Sensitization, Asthma, and Hay Fever

Pediatrics. 2016 Aug;138(2):e20160443. doi: 10.1542/peds.2016-0443. Epub 2016 Jul 11.

Abstract

Background: The hygiene hypothesis suggests that early-life exposure to microbial organisms reduces the risk of developing allergies. Thumb-sucking and nail-biting are common childhood habits that may increase microbial exposures. We tested the hypothesis that children who suck their thumbs or bite their nails have a lower risk of developing atopy, asthma, and hay fever in a population-based birth cohort followed to adulthood.

Methods: Parents reported children's thumb-sucking and nail-biting habits when their children were ages 5, 7, 9, and 11 years. Atopic sensitization was defined as a positive skin-prick test (≥2-mm weal) to ≥1 common allergen at 13 and 32 years. Associations between thumb-sucking and nail-biting in childhood, and atopic sensitization, asthma, and hay fever at these ages were assessed by using logistic regression with adjustments for sex and other potential confounding factors: parental atopy, breastfeeding, pet ownership, household crowding, socioeconomic status, and parental smoking.

Results: Thirty-one percent of children were frequent thumb-suckers or nail-biters at ≥1 of the ages. These children had a lower risk of atopic sensitization at age 13 years (odds ratio 0.67, 95% confidence interval 0.48-0.92, P = .013) and age 32 years (odds ratio 0.61, 95% confidence interval 0.46-0.81, P = .001). These associations persisted when adjusted for multiple confounding factors. Children who had both habits had a lower risk of atopic sensitization than those who had only 1. No associations were found for nail-biting, thumb-sucking, and asthma or hay fever at either age.

Conclusions: Children who suck their thumbs or bite their nails are less likely to have atopic sensitization in childhood and adulthood.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Asthma / epidemiology*
  • Child
  • Child, Preschool
  • Cohort Studies
  • Female
  • Fingersucking*
  • Follow-Up Studies
  • Humans
  • Hypersensitivity, Immediate / epidemiology*
  • Male
  • Nail Biting*
  • Rhinitis, Allergic, Seasonal / epidemiology*
  • Risk Assessment