Apply a Deterrent
If you visit the nail care aisle in the drugstore, you might have seen creams, oils or nail polishes specifically designed to stop nail biting. Since nail biting is an unconscious habit, the reasoning goes, you'll be startled into awareness when you taste the nasty solution on your fingers and stop what you're doing. Many of these products are also marketed to stop thumb sucking (yet another nervous habit, but one that rarely lasts into adulthood).
Ingredients for these products are typically hot, such as cayenne pepper extract, or bitter, such as denatonium saccharide. The latter is a nontoxic chemical compound often added to toxic products such as antifreeze to discourage children and animals from drinking it. Some people also try home deterrent solutions such as straight black pepper or bitters (an alcoholic beverage). However, these are more easily washed off, while commercial products are designed to last longer.
Some nail biters have successfully kicked the habit this way, while others get used to the taste or are too disgusted by it to keep it on their nails. Some people try other deterrents such as wearing a bracelet as a reminder not to bite them. Dentists can also fit you for a mouth guard if your nail biting is seriously damaging your teeth.
Putting something on your nails might still not be enough to make you stop biting, so perhaps a distraction is in order. Learn about that next.