Connection to Thumb Sucking
Astudy in the journal Pediatrics, published by the American Academy of Pediatrics, has found the common childhood habits of thumb sucking a nail biting can reduce the risk of adolescent and adult allergies.
Researchers followed more than 1,000 individuals from 5 through 32 years old, monitoring these two habits at ages 5, 7, 9 and 11. The subjects were tested for allergies at 13 using a skin-prick test and again at 32. Of all participants, 31 percent were frequent thumb suckers and nail biters, and those children had a lower incidence of allergic reactions than the others.
These results support a hygiene hypothesis suggesting that early exposure to microbial organisms reduces the risk of developing allergies.