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More on Allergies vs. Intolerances

January 31, 2009

Even though many people recognize only the Type I (IgE mediated) hypersensitivity as a true allergy, there are actually four types of allergies.

The Type II (IgG or IgM mediated) hypersensitivity is discussed here in this video from McGraw Hill. The example shown here is about blood types. The video shows how receiving a transfusion of the wrong type of blood causes cell death. This is why this type of reaction is called “cytotoxic” – it kills cells.

The Type III (IgG mediated) hypersensitivity is discussed in this video from McGraw Hill. The example shown here shows how kidney damage occurs due to the deposition of immune complexes in the body’s organs.

The Type IV (T cell mediated) hypersensitivity is discussed in this video from McGraw Hill. The example here shows how poison oak works, but this type of allergy is also responsible for rejection of donated organs.

All of these reactions are allergies, not just the Type I reaction, despite what you will read at many sites.

Intolerances are difficulties with food that are not mediated by any part of the immune system. Lactose intolerance is the most widely heard about. It is caused by the lack of a digestive enzyme that allows the body to break down the sugar that is found naturally in milk.

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