To dream that you are breathing rapidly indicates that you are experiencing some anxiety, tension, or fear concerning a new situation in your waking life.
To dream that you are breathing underwater represents a retreat back into the womb. You want to return to a state where you were dependent and free from responsibilities. Perhaps you are feeling helpless, unable to fulfill your own needs and caring for yourself. Alternatively, you may be submerged in your emotions.
To dream that you cannot breathe indicates that you are feeling exhausted. People who suffer from asthma often have dreams of not being able to breathe.
To dream that someone is breathing into your mouth suggests that you need to incorporate aspects of this person within your own self. If this person is no longer alive, then it means that he or she still lives within you.