The habit of biting one's nail could very well have started during childhood. About half of all adolescents bite their nails, but more than three fourths of those will give up the habit by age 35.

Nervous habits like these are unconscious behaviors that always repeat out of anxiety, stress or boredom. Nail biters have what doctors call onychophagia.

One problem with nail biting is that it's considered socially unacceptable; ragged, bitten nails aren't attractive.

Some people bite their nails so badly that their fingers bleed, or the nails are so stunted that there is almost no nail left.

But it's not just about having pretty hands in addition to having a negative impact on individual appearance, nail biting can also affect the health.

Psychotherapist Marisa Peer says ‘When you bite your nails you are putting these germs directly into your body, increasing your risk of infection.’ and ‘Nails are full of bacteria from everything you touch such as door handles, toilet flushers and money.’

This "frowned-upon" habit can be very well be a sign of perfectionism and not anxiety, as suggested by a recent study in Canada.

The habit was often a way of easing anxiety keeping at least one part of the body occupied while the mind wanders. Additional emotional triggers that can lead to nail biting are frustration and loneliness. Genes may also play a role as suggested by some research.

Biting fingernails can also be a symptom of a psychological condition, such as obsessive-compulsive disorder (OCD). People who wash their hands several times in a row or check the front door locks compulsively may also bite their nails as part of the same spectrum of behaviors.

Psychiatric disorders such as attention deficit hyperactivity disorder (ADHD), oppositional defiant disorder (ODD), separation anxiety disorder, or bed-wetting have also been associated with children who are into nail biting.

Regular nail biting that causes severe damage to the nail and surrounding skin can be considered a form of self mutilation, similar to cutting and related behaviors.

Leighton Denny, a leading cosmetic nail expert advices going for a professional manicure to reward oneself for breaking the habit and have one's nails painted red, so when the person sees red he can automatically think that red means "stop."