Alyssa Kendrick riding her pony Apollo. photo by Emily Williamson

Thumb-Suckers, Nail-Biters Less Likely to be Allergic to Horses

Correlation between common kid bad habit and no horse allergies

New research finds if children are thumb-suckers or nail-biters they are less likely to develop allergic sensitivities.

For kids with both ‘bad habits’, they are even less likely to be allergic to horses, grass, cats, dogs and airborne fungi.

The research just published in the Pediatrics journal was completed by researchers of New Zealand’s Dunedin School of Medicine. Professor Malcolm Sears of McMaster University’s Michael G. DeGroote School of Medicine assisted with the project.

“Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies,” said Sears. “While we don’t recommend that these habits should be encouraged, there does appear to be a positive side to these habits.”

The researchers were testing the idea that the common childhood habits of thumb-sucking and nail-biting would increase microbial exposures, affecting the immune system and reducing the development of allergic reactions also known as atopic sensitization.

More than 1000 New Zealand children’s habits of thumb-sucking and nail-biting were measured at ages of 5, 7, 9, and 11-years old. Atopic sensitization was measured by skin-prick tests at 13 and 32 years old.

The researchers found 31% of children were frequent thumb suckers or nail biters.

Among all children at 13 years old, 45% showed atopic sensitization, but among those with one oral habit, only 40% had allergies.

Among those with both habits, only 31% had allergies. The trend was seen in adulthood and showed no difference whether there was smoking in the household, ownership of cats or dogs, or exposure to house dust mites.

The study did not find associations between the children’s oral habits and development of asthma or hay fever.