Allergy is described as an exaggerated reaction of the immune system to foreign bodies and substances that are not harmful to normal non-allergic individuals. The response by the immunity process is exaggerated as it treats these foreign bodies as threats to the health of the body, in place of discarding and getting rid of them like it usually would. This reaction is feasible if a particular reaction to the immunity process is activated.

The mechanism of allergies begins with the so-called exaggerated reaction of the immunity process to antigens. Antigens are special substances that trigger the immune system to discharge its antibodies. Once an antigen invades the body, the immune system will endeavor to work out the nature of antigen by identifying whether it is dangerous or not. In individuals who have not developed allergies, all antigens are not harmful.

However, for individuals who had antigens which underwent previous sensitization, selected antigens are treated by the body as threats. Among allergic people, the invasion of an antigen will trigger a series of immune response referred to as allergic cascade. The outcome of which are hypersensitive reactions and symptoms characterizing the specific allergy or the specific body part affected by the antigen.

The antigen to which an individual is allergic to is known as allergen which comes in varieties of animal dander, foods, drugs, chemicals, pollens, dust mites and others.

Allergens can penetrate the body through various entry ways. These entry points are basically distinguished by the nature of the allergen. For example, nasal passages are the passageways for pollens, dust mites, dust, molds and other minute objects.

Allergens can also have a bearing on the body, but do not necessarily have to enter the inner body, through the contact with the skin or mucous tissue layers. Topical chemicals and substances are frequently the culprits of allergic responses on the skin. This hypersensitivity differs with other allergic responses as it only triggers cells of inflammation which are situated on the superficial layers of the skin and not the specific antibody that reacts to allergens- the IgE.

Nonetheless, for some substances, contact does not end with the skin, they often times seep through the underlying structures to cause more severe allergic responses. There are likewise irritants that are injected to the body. These typically consist of materials that are injected mechanically or chemical substances that insects carry. Lastly are the allergens that are ingested which compose of a variety of food that typically trigger allergic responses among humans, treatments and drugs. In over sensitive individuals, even water components may pose as allergens.

The allergic cascade happens in three phases. It begins with the encroachment in a common substance of the body's system. If the immune system detects it as harmless, it won't respond aggressively, ending in the antigen's elimination. Yet, if the immunity process detects it as a threat, it will produce IgE or immunoglobulin E, an antibody that reacts to allergens, in massive quantities. IgE will then plot the allergen as harmful and will establish immune side effects in succeeding encounters.

After sensitization comes another encounter with the antigen. By this occasion, the body has already developed exaggerated responses. Attributable to the discharge of some chemicals into the blood stream as it tries to eliminate the antigen, the body will experience the signs of the allergy.

These signs are the natural consequences of the immune response.