The Four Stages of Allergies

If you have hay fever, your symptoms don't take long to show up after you inhale the smallest amount of pollen. It takes mere minutes for your nose to begin running and for the sneezing (and perhaps wheezing) to start.

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Allergists call these "type I reactions" or "immediate hypersensitivity reactions." Allergic reactions to pollen, animal dander, mold spores, dust mites, and other common allergens are the result of a series of responses from your immune system.

The University of Pennsylvania Health System breaks this common type of allergic reaction into four stages.

The best way to prevent an allergic reaction is to identify the substance that causes it and avoid your "trigger" as best as possible.

Stage One: Sensitization

No one is born with allergies. Instead, the first step on the road to developing an allergy occurs when a person prone to allergies comes into contact with what is normally a harmless substance, such as plant pollen.

Often, such allergens first contact mucus membranes in the nose or another part of the respiratory system. Immune cells called plasma cells respond to the presence of the pollen or other allergen by making an antibody called Immunoglobulin E (IgE). The IgE molecule specifically recognizes the antigen.

Stage Two: Ready and Waiting

IgE antibodies latch onto immune system cells found in tissues of the respiratory tract, gastrointestinal tract, and skin. These tissue-bound immune cells are called mast cells. IgE antibodies also latch onto immune cells called basophils in the blood. Mast cells and basophils are equipped with IgE molecules that specifically recognize a particular antigen. These molecules do nothing until you inhale or ingest or come in contact with that particular antigen again.

So, in essence, your body receives the allergen and prepares for it to come in again. For people allergic to common allergens, this typically occurs within seconds of first contact.

Stage Three: The Battle

As soon as you are exposed to pollen again, the IgE antibodies attached to the immune cells bind to the allergen. This binding signals the mast cells and basophils to respond as if a dangerous intruder has invaded your body. The cells spew out over 30 chemicals, including histamine.

These chemicals produce inflammation, swelling, itching, redness, and other symptoms of common allergies.

Stage Four: Late Phase

Some people undergo a delayed response or a "late phase" of their allergic reaction, four to 24 hours after stage three. In these people, other types of immune system cells move to the tissues affected in stage three. These white blood cells seem to be attracted by some of the chemicals released by mast cells and basophils.

Unfortunately, the late visitors can release their own set of chemicals that can damage nearby tissues and perpetuate the reaction.

Preventing the Reaction

The best way to prevent an allergic reaction is to identify the substance that causes it and avoid your "trigger" as best as possible.

If that is not possible, an allergist can prescribe medications that can ease your symptoms. You might also eliminate or reduce the severity of your allergic response by receiving immunotherapy. Immunotherapy is a series of shots over the course of a few years to desensitize your immune system to a specific allergen.

About the Author

Boyan Hadjiev, MD, has been a practicing physician for five years. He is double board certified in Internal Medicine, (2003), and Allergy and Immunology, (2005).

Dr. Hadjiev graduated from University of Michigan with a BA in biology and an MD from Cleveland Clinic-Case Western Reserve School of Medicine.

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