Babies have the ability to suck on their thumbs starting from when they are still in the womb. While the act may be adorable — and parents may want their newborns to suck away instead of crying — as their child continues to grow, thumb-sucking is soon seen as a bad habit.

Thumb-sucking can prevent children's teeth from growing in straight, which means they will probably need braces when they get older. And this isn't the only habit kids can pick up as they continue to grow; many kids also bite their nails.

Even adults are guilty of biting their nails from time to time, but no parent wants their child to put germs in their mouth.

It's common for parents to tell their children not to do these two habits, but they may not be so bad after all. In fact, sucking their thumbs and biting their nails actually has a positive health outcome.

According to a study published in the journal Pediatrics, young children who suck their thumbs or bite their nails may be less at risk for developing allergies.

Researchers from New Zealand conducted a study that consisted of tracking the health of 1,000 children from Dunedin, New Zealand born in 1972 and 1973. The study lasted for five decades, where the researchers would assess the participants at various stages in their lives.

The researchers asked the parents of the participants about their kids' thumb-sucking and nail-biting habits when they were 5, 7, 9 and 11-years-old, as well as tested the kids for allergies via a skin-prick test at age 13 and then at age 32.

Other risk factors such as if the children were breastfed, if their parents had allergies and if they had pets were also taken into account.

According to the findings, children who both sucked their thumb or bit their nails when they were young were less likely to develop allergies by age 13 and then at 32 compared to those who only picked up one of the bad habits.

Children with at least one of the two habits were 40 percent less likely to develop allergies as an adult.

The study found that 38 percent of children who sucked their thumb or bit their nails developed at least one allergy. However, those who didn't pick up the bad habit had a 49 percent of having allergies.

The study did not find any correlation between the habits and the rate of developing asthma or hay fever.

That means that the "bad" habits may actually prevent allergies from developing later in life. This could be because that the children who are exposed to germs and dirt may build up an immunity to them, whereas those who are less exposed may have a larger influence on their immune system which means they can more easily develop allergies. This is what is known as the "hygiene hypothesis."

To be clear, the study doesn't suggest allowing children to suck their thumb or bite their nails as a way to prevent allergies, but it does mean that if they do occasionally, it might not be so harmful.

Source: Pediatrics

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