Most people have met someone with a significant fear of a particular object or situation, such as closed spaces (claustrophobia), heights (acrophobia), water (aquaphobia), snakes (ophidiphobia), or lightning (astraphobia).When a person has a persistent, irrational fear of an object or situation and a strong urge to avoid that object or situation, he has a "simple phobia" -- an inappropriately intense reaction triggered by a single stimulus.
The most common phobias are of specific animals and insects, of the natural elements, such as storms or water, of heights and of closed-in spaces.
The person with a specific phobia may react with mild anxiety or even with panic when confronted with the prospect of facing the fearful situation. However, his fear is not of his symptoms (as in panic disorder or agoraphobia) but of the situation itself, which he believes to be a dangerous one.
Some may fear that they will lose their senses and do something foolish. The person with a height phobia, for instance, might fear that he will forget what he is doing and accidentally leap off the cliff on which he is standing. Others with phobias fear that something will go wrong with their circumstances. The individual with a flying phobia might vividly imagine the tail falling off the plane, or the pilot losing consciousness with no one to take over, or the oxygen running out in mid-flight.
Such fears defy rational thinking. Most phobics know that they are being excessive and unreasonable in their thoughts, but this knowledge is of no use to them. The fearful thoughts come automatically in spite of rational thought and thus the phobic may believe the only recourse is to avoid the problematic area.
Read more at the site :http://www.cyberpsych.org/anxieties/phobias.php