1. Disease-Causing Bacteria
Your nails are the best place for bacteria developing including the potential pathogenic bacteria like Salmonella or E. coli.
So, when biting your nails you are actually inserting those bacteria in your mouth and through there in your entire body. From there it can cause various infections. The nails are harder to clean than your hands, which you can just wash with soap, so they are the perfect place for bacteria to stay.
2. Nail Infections
People who bite their nails are susceptible to paronychia, a skin infection that occurs around your nails. When you chew your nails, bacteria, yeast, and other microorganisms can enter through tiny tears or abrasions, leading to swelling, redness, and pus around your nail.
This painful condition may have to be drained surgically. Bacterial infections caused by nail biting are actually one of the most common nail problems, according to the American Academy of Dermatology (AAD).
3. Warts Due to HPV Infections
Another common disease among nail bitters are warts caused by human papillomavirus, or HPV. It it type of HPV that causes only warts on your nails and not the genital warts. The scary thing is that these warts can easily spread to your mouth and lips as you bite your nails.
4. Dental Problems
Biting your nails can cause problems with the manner in which your upper and lower teeth come together when you close your mouth.
Your teeth may shift out of their proper position, become misshapen, wear down prematurely, and become weakened if you bite your nails over time. The Academy of General Dentistry estimates that frequent nail biters may rack up $4,000 in additional dental bills over the course of their lifetime.
5. Impaired Quality of Life
People who chronically bite their nails report significantly higher quality of life impairment than those who do not, a study published this year found.
The level of impairment rises with time spent on nail biting, the number of involved fingernails and those who report visible nail abnormalities. Tension when trying to resist nail biting, suffering due to nail biting or nail-eating behavior also negatively influenced quality of life.
Source : www.fhfn.org