Disorders of the Immune System: Allergy

Allergies Happen When Your Immune System Raises a False Alarm

Sick woman blowing her nose
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The most common types of allergic reactions, including hay fever, some kinds of asthma, and hives, are produced when the immune system response to a false alarm. In a susceptible person, a normally harmless substance like grass pollen or house dust is perceived as a threat and is attacked.

Such allergic reactions are related to the antibody known as immunoglobulin E (IgE). Like other antibodies, each IgE antibody is specific; one IgE reacts against oak pollen, another IgE against ragweed.

The role of IgE in the natural order is not known, although some scientists suspect that it developed as a defense against infection by parasitic worms.

The first time an allergy-prone person is exposed to an allergen, he or she makes large amounts of the corresponding IgE antibody. These IgE molecules attach to the surfaces of mast cells (in tissue) or basophils (in the circulation). Mast cells are plentiful in the lungs, skin, tongue, and linings of the nose and intestinal tract.

When an IgE antibody siting on a mast cell or basophil encounters its specific allergen, the IgE antibody signals the mast cell or basophil to release the powerful chemicals stored within its granules. These chemicals include histamine, heparin, and substances that activate blood platelets and attract secondary cells such as eosinophils and neutrophils. The activated mast cell or basophil also synthesizes new mediators, including prostaglandins and leukotrienes, on the spot.

It is such chemical mediators that cause the symptoms of allergy, including wheezing, sneezing, runny eyes and itching. They can also produce anaphylactic shock, a life-threatening allergic reaction characterized by swelling of body tissues, including the throat, and a sudden fall in blood pressure.

Symptoms of Allergy

Allergy can present in many ways. Here are some typical symptoms of allergy:

  • tearing eyes;
  • runny nose;
  • stuffy nose;
  • allergic shiners (or dark circles around the eyes);
  • itching in the eyes, ears, throat and mouth.

What Are People Allergic to?

Allergies can be triggered by a number of things including the following:

  • mold
  • medications
  • latex
  • food
  • insect stings
  • animal dander
  • pollen
  • dust
  • plants and grasses

How Is Allergy Diagnosed?

If you think that you have allergies and are suffering from allergy symptoms, you should make an appointment with allergist, or physician who specializes in allergy treatment. Alternatively, you can request a referral to an allergist by asking your primary care physician.

An allergist diagnosis allergy using a combination of medical history and physical exam and confirms specific diagnoses using allergy testing. Allergy testing can be done using either a skin test or blood test.

How Is Allergy Treated?

Allergies are treated in a variety of ways, which include medicine, environmental changes and shots.

Here are some treatments for allergy:

  • antihistamines
  • decongestants
  • leukotriene inhibitors
  • steroid or anticholinergic nasal sprays
  • eye drops
  • mast cell inhibitors
  • dehumidifiers

Severe and life-threatening allergy can be treated using an auto-injector like an EpiPen. This auto-injector is loaded with epinephrine, a strong sympathetic stimulator.


For more information on Allergies, visit theĀ Allergy Site, which comprehensively explores this topic.

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