The human body has a complex immune system which helps it to fight infection. When infection attacks the body the immune system is triggered to produce antibodies. These antibodies have an individual ‘key’ to fit each individual infection. After exposure to a virus or bacteria, the immune system remembers this ‘key’. This protects the body from repeated infection from the same bacterium or virus. People who have allergies have an immune system that reacts to a usually harmless substance in the environment. This substance (pollen, mold, animal dander, etc.) is called an allergen.

What Happens During an Allergic Reaction?

The most common mechanism by which an environmental substance causes this kind of reaction involves antibodies, which are proteins formed by the immune system. The normal function of antibodies is to protect the body from infection by attacking and killing organisms like viruses and bacteria. In the case of allergy, the antibody is called immunoglobulin E, or IgE, and, rather than attaching itself to microorganisms, the antibody binds to normally harmless substances like pollen, dust mites, and animal danders.

Once IgE is formed in the bloodstream, it seeks out and binds to a type of cell called a mast cell, which is located in the mucous membrane of the eyes, nose, lungs, and gastrointestinal tract as well as skin. If the person is then re-exposed to that same allergen, the mast cell is triggered within a few minutes to release a variety of chemicals, including histamines, leukotrienes, and prostaglandins. These chemicals, which are also referred to as mediators of the allergic response, are responsible for the symptoms that patients develop after exposure to allergens.

Symptoms of an Allergic Reaction

Common symptoms of an allergic reaction to inhaled or skin allergens include:

• Itchy, watery eyes
• Sneezing
• Itchy, runny nose
• Rashes
• Feeling tired or ill
• Hives (a rash with raised red patches)

Common allergies and their symptoms can manifest anytime and anywhere so if you have allergic reactions to some types of foods, smell, pollen and others, you need to be very careful and avoid your allergy triggers. Note that some common allergies and their symptoms can cause some complications in your body. Once medical complications happen, danger comes in. Allergies are often tricky to diagnose and treat for a number of reasons. First, people display highly idiosyncratic reactions, which take on a diversity of symptom pictures. Allergies may also show up suddenly in someone with no previous history of sensitivity to an allergen. The converse may also happen; people with a previous sensitivity to a specific allergen may find themselves less reactive after a time.