Every person reacts differently to stress. And every person has a different habit typically for stress. One such habit is nail biting and it can very much stick through till adulthood. Scientists claim that kids whose parents are nail biters are likely to form a habit of nail biting too. Nervousness or stress might make certain people bite their nails and this particular habit of theirs makes it easy for the opposite person to detect that the person is stressed out about something. And this isn't one of those conscious things that people do, nail biting which being nervous or stressed comes without thinking, when their mind is wondering about the thing that's bothering them.
This particular habit doesn't only damage your nails but also tends to give you infections since your nails are always exposed to bacteria and viruses which go in to your mouth and face. Since you keep biting your nails too often, it leaves the skin around your nails sore and damaged almost all the time.
This leads to abnormal nail growth as your nails may stop growing the way they're supposed to. It might also spoil your smile as biting nails can chip or crack your teeth and you might also develop a jaw problem eventually. It can also make you fall sick as the bacteria in the nails transfer to your mouth and leads to many infections.
Hence, you should keep your nails trimmed and short so that you don't end up biting the extra bit all the time and chew on it unnecessarily. You should also identify the triggers of your nail biting and see if you're biting them out of boredom or anxiousness. There are chances that you might be hungry as well. Once you identify the trigger, work up on it and bring a solution to it rather than sitting and biting on your nails as it's not going to do you any good. Keep your hands busy in some or the other activities. Fiddle with objects so that you don't keep biting your nails.
There are various other medical ways to get rid of biting nails but for starters you could try these out.