Environmental Allergy

Allergies were thought at first to be caused by an improper activation of the antibody class called Immunoglobulin E (IgE). But it later became clear that several different disease mechanisms were implicated, with the common link being a disordered activation of the immune system in one or another of its many pathways. A new classification scheme was designed by P. Gell and R. Coombs to reflect what were then rebaptized hypersensitivity reactions. The word "allergy" was then restricted to Type I Hypersensitivity, which is caused by the classical IgE mechanism.

Type I Hypersensitivity is characterised by excessive activation of mast cells and basophils by IgE, resulting in a systemic inflammatory response that can result in symptoms as benign as a runny nose, to life-threatening anaphylactic shock and death.

Allergy is a very common disorder and more than 50 million Americans suffer from allergic diseases. Allergies are the sixth leading cause of chronic disease in the United States, costing the health care system $18 billion annually.

...More at Wikipedia

Related Links:

• US National Library of Medicine
• Mayo Clinic

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