Biting Your Nails, Part 2

I do not expect any long-term nail-biters to be pleased by being reminded (yet again) about the "bad" side of their habit. I know it's a deeply ingrained habit, and almost impossible to quit.
06/10/2010 11:33am ET | Updated November 17, 2011
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I'd like to revisit biting your nails for this week's post. The reason I am revisiting that topic is because my last post on the subject not only seemed to generate quite a response within the community, but it also elicited some definite passion from several readers.

Before I start, I want to state up front that I do not intend to make light or simplify what could be a problem for someone. As a dentist, I use this blog to post what I hope is helpful information and/or my feelings on issues, mostly (but not always) as they pertain to your mouth. But I have no interest in treating this blog as anything more than my own professional opinion -- read here for information from a professional dentist's mind, not for the last word on all things medical. For example, if I write that I think mouthwash can cause oral cancer, it's because my professional experience and knowledge has led me to believe it. I may (or may not) look around for a few articles on the topic that I can mention, but I'll admit I did not personally spent months alone in my lab, painstakingly researching that topic. Does that mean you should listen to (or dismiss) what I have to say? That's your choice. If I got even one person to give up mouthwash with that article, then I'm happy.

I also do not pay much attention to what I call the "exception argument" (nor should you). I see nail biters everyday in my office, and I know -- beyond any doubt -- that in an overall sense, it will hurt your teeth. Now, does that mean everyone who bites their nails will hurt their teeth from their nail biting? No, of course not. It's similar to smoking -- there's always someone who knows someone whose grandfather smoked until he was 90, and it never affected him. While I'm happy for that person, that doesn't mean smoking isn't harmful, does it? That's what I mean by the exception argument.

I go by three things here -- what I have learned in my training, what I continue to learn, and what I see every day in my life as a professional cosmetic dentist -- in general terms, those three things shape my opinion.

Ok, all that said, let's get back to nail biting.

I posted earlier that nail biting is un-hygienic, and could get you sick. I'm not the only person who feels this way -- a quick search of "biting nails germs" (or similar) will point you to hundreds of articles and topics on the subject, almost all of them coming to the same conclusion. A study done by renowned microbiologist Dr. Anthony C Hilton concluded that 25% of men, and 15% of women have a harmful bacteria called enterobacteriaceae living under their nails. Enterobacteriaceae is associated with gastrointestinal disorders, diarrhea, and vomiting. Again, findings like these do not suggest that everyone who bites their nails will throw up, but it does illustrate that there can be harmful bacteria under your nails.

Another expert -- Dr. David Katz of Yale University -- conducted an experiment with his students to test bacteria grow under the fingernails. He swabbed samples from several students (with nails of varying length), and then let the bacteria grow. He also then took swabs after they washed their hands. The results were that after 3 days of growing time, short painted nails have least amount of bacteria growth. Conversely, long unpainted nails had the most growth. The reason is fairly simple: short fingernails are easier to clean. Also, nail polish has several chemicals (including formaldehyde) which minimize bacteria growth (errr, you probably don't want to be chewing on painted nails, however -- last I checked, formaldehyde isn't in any of the food groups J )

Now, as mentioned by Katz's study above, hand-washing plays a part here. If you are a really good / thorough hand washer, your chances of having harmful bacteria under your nails is lessened greatly (using a nail brush will help.) Also, your job may factor into it -- I don't think it's a stretch to assume that a chicken farmer will have more germs under his or her nails than a swimming instructor (that might depend on what's in the pool, of course!)

Lastly, let's talk about the teeth again. A few comments took exception to my stating that nail biting can damage teeth. And that's fine -- I'm pleased that those people have not had any ill effects (again, it's a certainty that not everyone will.) But, as I stated earlier in this post, seemingly every day I see the damage that nail biting has caused. Chipped, weak teeth; damaged enamel, etc. I'm a cosmetic dentist, so many of my patients are in my chair to look better, so I likely do see a higher percentage of "damage" issues than the norm, but it does not change the fact that I personally can draw a direct correlation to nail biting. I'm sure someone will mention correlation does not always mean causation (and I agree -- after all, 100% of murderers drink water. Does that mean water drinking leads to murder?) However, correlation does not automatically mean "ignore" either. And I've seen too much first-hand to ignore this -- in my mind (and professional opinion), it's a fact that nail biting can hurt your teeth. In looking at some old magazines the other day, I came across this blurb: "Nail-biters also can damage their teeth", adds Stephen J. Chu, D.M.D., director of the advanced aesthetic program at New York University College of Dentistry in New York City. "When you bite your nails, you twist and tear, and that can chip enamel." (Shape magazine, Nov 2002)

The above is simply food for thought in regards to nail biting. I do not expect any long-term nail-biters to be pleased by being reminded (yet again) about the "bad" side of their habit. I know it's a deeply ingrained habit, and almost impossible to quit. To many folks, nothing short of that miracle cure will be of interest. I get it. But I also enjoy blogging and reading your comments (both good and bad), and feel I have a responsibility to share my feelings and knowledge as best I can. And I hope this has been of interest to you.

Until next time, keep smiling.

Hilton -

Katz -

Interesting Link -