Illness anxiety disorder as the name specifies it is an over anxiety towards ones health but have no physical problems. They are more preoccupied and anxious of having an illness if there is a health issue in the family history.
Illness anxiety disorder may be due to family history, serious illness in the past and afraid of reoccurrence of the same and poor knowledge of the diseases. This usually starts at middle age and get severe as the age prolongs.
Cognitive behavior works well for the treatment of illness anxiety disorder by counseling them with the beliefs and making them understand the level of the disease.