This fits with the “hygiene hypothesis”, which says that when children are exposed to germs early in life, their immune system gets trained to attack germs, rather than attacking itself as we see in allergies, asthma, and eczema (of note, the researchers didn’t find protection against asthma or hay fever, and didn’t report a measure of eczema). From the whole group, 31% of the children had one of these habits during their childhood, between 5 and 11 years old.
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The study, published this month in the American Academy of Pediatrics, observed more than 1,000 participants from childhood to adulthood.
Among all children at 13 years old, 45 percent showed atopic sensitization but among those with one oral habit, only 40 percent had allergies.
1,037 children in New Zealand born between 1972 and 1973 were given allergic tests at age 13 and then again at age 32.
The researchers also took an array of other factors such as gender, parental history, and pet ownership into consideration; however it was found that these factors hardly affected the result outcome, Perf Science reported. With the help of answers, Lynch and study main author Bob Hancox managed to collect the data about thumb-sucking and nail-biting.
“Nail biting can cause damage to nails and skin and expose the fingers to infections”, he said.
They noted the ones who both sucked their thumbs and were into nail biting had even lesser chances of contracting allergies (31%). Most children stop sucking their thumbs between the ages of 2 and 4.
Researchers used a skin-prick test to determine whether there was an allergic reaction to general allergens.
The suggestion that thumb sucking and nail biting may reduce the risk of allergies later needs to be supported by different studies in different geographical regions around the globe, said Emmanuel Prokopakis of the University of Crete School of Medicine in Greece, who was not part of the new study.
Stephanie Lynch, a student at the Dunedin School of Medicine, had the idea for the study.
While 38% of children who either sucked their thumbs or were nail-biters were found to have allergies, a shocking 49% of children who had allergies were neither thumb-suckers nor nail-biters. Nail biting and thumb sucking are normally two big no-nos for toddlers and young children, but could these bad habits have a surprising upside?
Don’t run off to stick your toddler’s thumb in her mouth just yet.
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If your child is a thumb sucker or a nail biter past an appropriate age, you should look for healthy ways to discourage the behavior. She was inspired by the 1989 ‘hygiene hypothesis.’ This theory suggested that people who were not exposed to germs and allergens as children would be more likely to develop allergies and autoimmune disorders as adults.
