Anyone who actually suffers with this compulsion will know that it tends to be regarded as something of a personal foible by people who don't have it. Non nail-biters regard it with distaste but will not appreciate how serious a problem it can be for someone who has the compulsion. Nail biting can range from desultory nibbling, to actually chewing the nails literally to the quick, and then chewing the surrounding skin in extreme cases.
The problem is that most of the time you are only vaguely aware, if at all, that you are actually doing it. This is because it is usually closely tied to being very abstracted and lost in thought. In fact it is generally an aid to this sort of self absorption and can be synonomous with beginning to mentally chew over some current problem or anxiety.
If you are at all concerned with your appearance. If you have to attend meetings at work, the effects of nailbiting can become a debilitating source of embarrassment to you. You may actually feel you want to avoid certain situations where this is highlighted.
The approach with hypnotherapy is to begin to appreciate that you have to make friends with the nailbiting part of yourself rather than demonizing it. This allows you to make the whole process more conscious.When you begin to reintegrate that rather dissociated part of yourself and bring it more fully into your conscious mind, you are much more aware of the triggering that sets you off. Direct suggestions in the trance state, will create an alertness that in itself tends to neutralize the behaviour as soon as it begins.The aim is to make you so conscious of what you are doing when you begin to bite your nails, that the only way you can continue is if you make a deliberate conscious decision to do so.
Often nail-biting will yield to one or two sessions of hypnotherapy.