An epidemiological study of around 1,000 children born between 1972 and 1973 in New Zealand suggests that those who bit their nails or sucked their thumbs when they were little were less likely to develop allergies as they grew up.
Children Who Bit Their Nails and Sucked Their Thumbs:
The parents were asked to assess the youngsters’ nail biting and thumb sucking behavior at various ages–5, 7, 9 and 11. The children were then tested for allergies when they reached 13 years of age and again when they were no longer children, but adults of 32.
Who Had Allergies?
Allergies were common by the time this cohort reached adulthood. Thirty-eight percent of the kids who had sucked their thumbs or bitten their nails tested positive for allergies. That compared to 50 percent of children who had not.
The researchers are not recommending that parents encourage either thumb sucking or nail biting, but trying to break a child of such habits may no longer be so urgent.
Pediatrics, online, July 11, 2016
The Hygiene Hypothesis:
This research is consistent with the “hygiene hypothesis.” That theory holds that babies exposed to more germs train their immune systems differently. Most of the research has looked at whether families have pets in the home or farm animals nearby. Children who constantly put their hands in their mouths are also exposing their immune systems to lots of germs.
To learn more about the hygiene hypothesis and possible ways to counteract our super-clean society, you may wish to listen to our hour-long interview with Maya Shetreat-Klein, MD, author of The Dirt Cure: Growing Healthy Kids with Food Straight from Soil.
