An allergic cascade is the sequence of chemical releases that takes place in response to an allergen. The end result of this chain is the release of histamines and other chemicals that bring on typical allergy symptoms.

Individuals must first become sensitive to an allergen before an allergic reaction can take place. This process involves the immune system mistakenly perceiving an allergen to be a threat and producing a specific type of antibody to later recognize that allergen.

The allergic cascade occurs when an individual who has been sensitized to a specific substance encounters that allergen again. Links in the chain that make up an allergic cascade include:

• Proteins in the allergen, which are mistakenly recognized as threatening.
  
  
• The production of specialized antibodies to deal with this perceived threat. These antibodies attach to mast cells, which contain a variety of chemicals, including histamines.
  
  
• Histamines circulate in the body causing many of the symptoms associated with an allergic reaction, affecting the nose, lungs, throat, skin and digestive tract.

The body’s reaction to the allergic cascade depends on the individual and the allergen. Some symptoms appear immediately or within minutes, while others appear after several hours. Symptoms typically include itching, runny nose, hives, nausea, wheezing and diarrhea.

Those individuals who react most severely to allergens may be at risk for anaphylactic shock, which is a potentially life-threatening condition involving shortness of breath, a sudden drop in blood pressure and shock.