Your mom always told you that nail biting was a bad habit (likely while swatting your hands away from your face). And while sticking your fingers in your mouth isn't something we encourage, it turns out that nail biting might not be all bad, according to a new study published in Pediatrics.

Researchers found that kids who nibbled their nails were less likely to get allergies and had stronger immune systems overall. Nail biting allowed bacteria and pollen trapped under the kids' fingernails to get into their mouths, boosting their immunity. Basically, dirty fingernail chewing worked a little like an all-natural (and slightly icky) vaccine.

"Our findings are consistent with the hygiene theory that early exposure to dirt or germs reduces the risk of developing allergies," Malcolm Sears, Ph.D., a professor of medicine at McMaster University in Australia, lead researcher said in a press release. "While we don't recommend that these habits should be encouraged, there does appear to be a positive side to these habits."

The "hygiene theory" says that because we've all worked so hard to sterilize our homes, offices, and public spaces, we've actually made them too clean and our immune systems are suffering from lack of dirt. It appears that what doesn't kill us does make us stronger, especially when it comes to germs.

Still, nail biters are more likely to get illnesses ranging from the common cold to hepatitis and are also exposed to harmful pollutants in nail polish and the environment. Plus, "your fingernails are almost twice as dirty as your fingers. Bacteria often gets stuck under the nails, and can then be transferred to the mouth, causing infections of the gums and throat," as Michael Shapiro, M.D., medical director and founder of Vanguard Dermatology in New York City told us in 10 Terrifying Reasons to Stop Biting Your Nails.