If you've got a little thumb sucker or nail-biter, you can stop nagging them about it now.
One study shows that both icky habits may have some very surprising health benefits.
Researchers have discovered that children who nibble their nails or suck their thumbs may reduce their risk of developing allergies as adults by one fifth. For children that had both habits, the risk was reduced to just one third.
Why? Well, apparently kids who suck their thumb or bite their nails are unwittingly ingesting a specific beneficial type of bacteria that lives under the fingernails.
The finding emerges from the long-running Dunedin Multidisciplinary Study, which has followed the progress of 1,037 participants born in the New Zealand city in 1972-1973 into adulthood.
Parents of Dunedin Study members reported their children's thumb-sucking and nail-biting habits when their children were ages five, seven, nine and 11 years-old.
The members were checked at ages 13 and 32 years old for atopic sensitisation, defined as a positive skin prick test to at least one common allergen. At age 13, the prevalence of sensitisation was lower among children who had sucked their thumbs or bit their nails (38 percent) compared with those who did not (49 percent).
The effect persisted and was still apparent when the participants were tested again at 32.
Dr. Robert Hancox, an associate professor of respiratory epidemiology at the University of Otago in New Zealand believes the findings "support the "hygiene hypothesis", which suggests that being exposed to microbes as a child reduces your risk of developing allergies,"
Despite these findings, the researchers do not suggest that children should be encouraged to take up these habits. Any beneficial bacteria is likely to share that piece of real estate with other goodies such as influenza, Streptococcus and the common cold, not to mention staphylococcal organisms, salmonellosis and hepatitis A.
Medical student Ms Stephanie Lynch says "although thumb-suckers and nail-biters had fewer allergies on skin testing, we found no difference in their risk for developing allergic diseases such as asthma or hay fever."
