Anxiety Disorders is a broad category of disorders which contains a separate chapter in DSM-IV-TR. Agoraphobia and panic attacks are the subtypes of anxiety disorders. Although, both of theseorders are separate entities yet, there is a unique relevancy between the both. In most of the clients, panic attacks (fits of intension anxiety) leads to Agoraphobia (fear of crowded or public places).
Now, I will describe the features of both disorders separately. Panic attacks are an expression of anxiety such as obsessive compulsive disorder, social phobia, and hydro phobia is an expression of mental anxiety. These attacks occur like fits which last for ten minutes at least. During this fit of ten minute, individual experiences accelerated heart beat, sweating, breathing difficulty, chest pain, nausea, dizziness, lack of control over one's self, fear of dying, numbness and hot or cold flush. Feelings of unreality (Derealization) and feelings of detachment from one's own self (Depersonalization) can take place during fit. Agoraphobia is the condition that comes after panic attacks.
If someone around you is experiencing an attack, you must understand different patterns of attacks to manage them accordingly. In order to explain different patterns of attack, I will use the example of a person who has extreme fear of dogs. In the first condition, person may experience an attack without confrontation to a dog. He may think about the possibility of dog bite and get panic, without any probable reason (we know that dog is not present in the environment at this time). These are unexpected attacks. Second kinds of attacks are situationally bound panic attacks. These are the attacks in which anxiety provoking stimulus is present in the environment. In such cases, person experiences an attack whenever he watches a dog. Situationally predisposed attacks are considered as the third types of attacks. In such attacks, person may or may not experience an attack after facing anxiety provoking stimulus in the environment.
An important thing to keep in mind is the discrimination between panic attack and panic disorder. Panic attack is a discrete episode or fit. A person may experience this fit for once. We diagnose panic disorder when a person experiences panic attacks repeatedly. These attacks change his overt behavior, he becomes concerned about reasons of these attacks and feels that, he is going crazy. Now this is responsibility of close ones to evaluate symptoms, and consult a psychologist as soon as possible.
Now, I will move towards the relationship between agoraphobia and panic attacks. You can imagine a person who gets an attack when he watches a dog or think about mishap related to dog. A person may experience these attacks when he watches dog in the street, or in case of unexpected attacks, he does not know when he will experience an attack. As a consequence, individual prefers to stay at home, because his visit may confront him with anxiety provoking stimulus. Moreover, he starts avoiding public places, because he can get the attack in front of other people, which will be embarrassing for him.
Last thing is to consider the age of sufferer. Empirical researches show that children with panic attacks do not exhibit cognitive symptoms (eg, going crazy, Depersonalization and Derealization). People tend to avoid treatment of panic attacks without they develop agoraphobia. So whenever you observe Agoraphobia in any nears and dears, try to seek psychologist's consultation at first preference.