Nail biting does far more than ruin your fresh manicure—from bacterial infections to lip warts, these gruesome truths will inspire you to nix the habit for good.
Credit: Getty Images/Jamie Grill

Nail biting (onychophagia if you want to be fancy about it), may seem pretty harmless, ranking somewhere between picking your nose and examining your earwax on the scale of "gross things everyone does but won't admit." In fact, up to 50 percent of us will gnaw our nails at some point in our life, according to a study from the University of Calgary.

But why is chewing our fingertips so compelling and even satisfying? It turns out it has nothing to do with your nails and everything to do with your feelings, says Fran Walfish, Ph.D., a psychotherapist in Beverly Hills, author, and psychology expert on The Doctors (CBS).

"Fingernail biting, like drugs, alcohol, food, sex, gambling and other addictive behaviors, is a way of not dealing directly with uncomfortable feelings," she says. In other words, when you're in an uncomfortable situation, your body feels like it needs to do something to deal but if you can't (or won't) address the discomfort directly, you can temporarily soothe yourself with a distracting and calming behavior, like nail biting, she explains. Taken too far, the nervous habit can even turn into "pathological grooming," an obsessive-compulsive behavior that you may feel like you have to do to calm down, she adds.

Even though it's not on the level of doing drugs or binge eating, nail biting can be detrimental to your health—in some ways that may surprise you. From making you sick to cracked teeth, these 13 science-backed facts are scary enough to make you nix the bad habit for good. (Don't worry we have tips for overcoming your nail-biting habit, too.)

Nasty Infections

There's a reason cops and coroners always clean out under a victim's nails on crime shows: Fingernails are perfect catch-alls for dirt and debris. When you chew yours, you're giving all those germs a one-way ticket to your insides, says Michael Shapiro, M.D., medical director and founder of Vanguard Dermatology in New York City. "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."

Chronic Headaches

Nail biting is the gateway drug for tooth grinding and jaw clenching, according to a study published in the Journal of Oral Rehabilitation. But the real culprit here is anxiety: People who deal with their worries by biting their nails are more likely to also have bruxism (grinding your teeth) and jaw clenching, both of which can lead to long-term oral problems like TMJ syndrome, chronic headaches, and broken teeth. (Related: How to Stop Grinding Your Teeth)

Painful Hangnails

Normal hangnails are painful but have you ever had one that became infected? It'll have you typing with your knuckles. "Chewing exacerbates dry skin, making peeling worse and leading to more hangnails," explains Kristine Arthur, M.D., an internist at Orange Coast Memorial Medical Center in Fountain Valley, CA, adding that people who chew their nails often use their teeth to peel off hangnails, leading to a tear becoming longer and deeper. (Related: 7 Things Your Nails Can Tell You About Your Health)

And if you get really aggressive, gnawing on your cuticles or biting your nails to the quick, you can open up small sores on your fingers or cuticles, allowing dangerous bacteria to get inside and cause them to become infected. Prevention is your best defense against hangnails so moisturizing regularly can help, she adds.

Coughs, Sneezes, and...Hepatitis

It's not just bacteria that are a potential problem. Nail biting also increases your risk of getting viruses. "Think of every single thing you touch during your day, from doorknobs to toilets," says Dr. Arthur. "Germs can live on these surfaces for hours, so when you stick your hands in your mouth, you're exposing yourself to cold and flu viruses, or even serious illnesses like hepatitis." (Related: How to Avoid Getting Sick During Cold and Flu Season)

Toxic Poisoning

Nail art is a huge trend in the beauty world right now but all that gel, glitter, jewels, dip powder, and holographic polish are concerning for nail biters because, you know, you're basically eating them, says Dr. Arthur. "Regular nail polishes have plenty of toxins themselves, but gel polishes have chemicals that are specifically approved only for topical use, meaning they're not meant to be ingested," she says. (Related: 5 Ways to Make Gel Manicures Safer for Your Skin and Health)

It may take a long time to build up a toxic level in your system, but do you really want to take that chance? (Until you quit your nail-biting habit, use try these clean nail polish brands free of formaldehyde and other harmful ingredients.)

Warts On Your Lips

Facial warts aren't just for wicked witches: Warts on your fingers are caused by the human papillomavirus or HPV, and nibbling your nails can spread that virus to your other fingers, your face, your mouth, and even your lips, explains Dr. Arthur.

Fungal Growths

There's a fungus among us? There's nothing cute about fungi on your fingertips. "Nail biters are particularly susceptible to paronychia, a skin infection that occurs around your nails," says Dr. Shapiro. He says that chewing your nails can allow yeast, fungi, and other microorganisms to set up shop under and around your nails, leading to swelling, redness, and even oozing pus. Yikes. (Related: 5 Common Fungal Skin Infections You Can Pick Up at the Gym)

Cracked and Worn-Down Teeth

Biting isn't just bad for your fingers, it's also bad for your teeth. "It can interfere with proper dental occlusion, or the manner in which your upper and lower teeth come together when you close your mouth," says Dr. Shapiro. "Plus, your teeth may shift out of their proper position, become misshapen, wear down prematurely, or become weakened over time."

Weird-Looking Fingers

Nail gnawing not only ruins your manicure but can make your actual nails look pretty rough—and we're not just talking about the stubby, ragged edges. Constantly biting your nails puts pressure on the nail wall which, over time, can actually change the shape or curvature of your nails, says Dr. Arthur. You could cause them to grow in unevenly or with bumpy ridges, she says. (Related: This Woman's Curved Nail Turned Out to Be a Sign of Lung Cancer)

Painful Ingrown Nails

Most of us are familiar with ingrown nails on our toes but did you know that biting your nails can lead you to get them on your fingers as well? Worst-case scenario, ingrown nails can get so bad they cause infection and can even require surgery, says Dr. Shapiro. Best case, you still get all the swelling, redness, and pain you know and loathe while you wait for them to grow out.

For all of those not-so-pretty physical side effects of nail-biting, the bad habit can also impact you psychologically. Here are some of the ways biting your nails can affect your mental health:

Low-Key Self Hatred

There are enough things in this world to make you feel bad about yourself (oh, hello, social media!), you don't need to add your own fingertips to the list. If you think of nail-biting as a bad habit then every time you catch yourself in the act or see your ragged tips, you're reminded of your lack of self-control, which can lead to lower self-esteem overall, says Walfish. In other words, not being able to stop biting your nails can make you feel like a failure.

Broadcasting Your Anxieties

Nail biters often put out a self-conscious vibe. "Most people bite their nails to seek comfort or relief from a negative emotional state, such as distress, shame, anxiety, or boredom," says Mary Lamia, Ph.D., clinical psychologist and professor at the Wright Institute in Berkeley, CA. "In a sense, nail-biting attacks the self, which tends to result in publicly exposing one's feelings of shame and of disgust about the self."

Angry Outbursts

Many people bite their nails as a way to deal with frustration, anger, and boredom but this habit can actually add to your frustration, making you want to chew more—creating a vicious cycle of repetitive behavior and anger, according to a study published in the Journal of Behavior Therapy and Experimental Psychiatry. Biting your nails may provide short-term relief from frustrating or boring situations but over time will only make those feelings worse.

How to Stop Biting Your Nails

Convinced you need to quit nibbling? Going cold turkey on biting your nails can be harder than you think, especially if you have been using it as a coping technique since you were a child, says Dr. Walfish. But take heart, it can definitely be done! (Related: The Best Way to Successfully Quit a Bad Habit for Good)

"At the root of all pathological grooming behaviors is simply a habit and you can change habits with simple behavior modification techniques," she explains. First, you need to start with addressing any underlying mental health issues like chronic anxiety or depression that may feeding your need to chew, she says.

Second, come up with an alternate, less damaging behavior you can do when you do feel anxious, nervous, or bored, she says. For example, some people like to do something to occupy their fingers like crocheting or playing with a fidget toy.

Third, do something to call your attention to the nail-biting when you're tempted to do it. Some women get fancy manicures with jewels, acrylic nails and other things that are hard or gross to chew on; others use a pretty ring or bracelet that will catch their eye when they raise their hand to their mouth; while some have found success placing a rubber band around their wrist and snapping it whenever the temptation arises.

Lastly, give yourself a fun reward when you reach one week and one month, bite free. The trick is to find what motivates you personally, adds Dr. Walfish.

If those tricks don't help and you still find yourself unable to quit nail biting, it may have become a full compulsion, she says. In this case, see your doctor as you can use medication, cognitive behavioral therapy, or a combination of the two to combat the urges.