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

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

Author information

1
Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand; and.
2
Firestone Institute for Respiratory Health, Michael de Groote School of Medicine, McMaster University and St Joseph's Healthcare, Hamilton, ON, Canada.
3
Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand; and bob.hancox@otago.ac.nz.

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.

PMID:
27401101
DOI:
10.1542/peds.2016-0443
[Indexed for MEDLINE]
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