Self-Soothing

• Stress can make a person feel as if she needs to self-soothe, and sometimes biting her nails helps them feel better because it has a calming effect on her nervous systems and reduces levels of stimulation as described by BrainPhysics.com. Fingernails are readily accessible to a stressed individual. Effects of this cause are developing a dependency on the biting and not being able to find alternative, healthy ways to cope with stress.
  
  

Increasing Stimulation

• BrainPhysics.com also states that although one cause of nail-biting is to reduce stimulation, nail biting can occur for the very opposite reason -- not enough stimulation for their nervous system when a nail-biter is bored or inactive. It is usually an unconscious decision, unlike the more likely conscious decision of someone who bites his nails to self-soothe.
  
  

Perfectionism

• A conscious reason a person bites his nails is his fixation on examining his nails or fingers and finding irregularities, and wanting to fix it. By biting his nails, person hopes that he can improve the way his nails look. However, biting his nails often causes the opposite effect and makes his nails look worse than if he left his nails alone, which can cause anxiety and stress. The nail-biter may look to self-soothe, which perpetuates the nail-biting process.
  
  

Other Effects

• A chronic and extreme nail-biter can experience bleeding, bruises, infections and sometimes permanent damage to her fingers. If a nail-biter cannot get herself to stop her biting willingly, she may need medication or therapy to help curb any disorders that may be causing the nail-biting. If the nail-biter doesn't realize what he is doing, he may be unknowingly putting germs in his mouth as bacteria can be gathered and stored under nail beds and as a result can become very sick as the Nail Biting Swish explains. Nail-biting can become a focus of someone's life and can affect relationships and work, especially if she is sharing equipment or shaking hands.