August 24, 2008

Terminology of Allergies

Why it should be called “Non-IgE Allergy

The immune system is very complex and only partially understood. There are several different kinds of immune system reactions. Some of the better understood reactions involve immunoglobulins.

Immunoglobulins are antibodies present in the blood and tissues of all vertebrate animals. They are called IgA, IgD, IgE, IgG, and IgM. IgE reactions are unique in that IgE antibodies reside in the tissues on mast cells (Other Ig antibodies circulate in the blood and lymph systems). When IgEs encounter the molecules to which they are sensitized, they can trigger violent muscle contractions and inflammation. This is what causes the life-threatening reaction anaphylactic shock, as well as less severe reactions of inflammation and congestion.

An allergy is an immune system reaction to a normally benign substance, such as pollen or food. The allergy/immunology establishment acknowledges and treats only IgE allergy reactions. They use the word "allergy" to mean only IgE reactions, which is not the way the word was defined in 1906.

There can also be allergies that do not involve IgE, but do involve other immune system components, such as the other immunoglobulins or T-cells. These can also become sensitized and react to normally benign substances, just like IgE.

Since the allergy/immunology establishment hasn’t accepted the existence of this type of allergy, they haven’t agreed on what to call it either. Some of the terms used by medical professionals include:

Immune sensitivity
Food sensitivity
Food intolerance
Hypersensitivity
Hypersensitivity reaction
And by far the most confusing,
“Non-allergic _____________”

examples: “non-allergic rhinitis”, “non-allergic asthma”

The A/I establishment uses the term “allergy” to refer only to IgE-mediated reactions. They resist calling immune reactions that are not IgE-mediated an “allergy”, and this is why they use other, less clear and confusing terms for it.

Most people understand the word “allergy” to mean the symptoms of illness without being sick, caused by a normally harmless substance. Calling non-IgE allergies by other terms (especially “non-allergic __________”) causes a lot of unnecessary confusion for patients and other non-allergists. Managing allergies is already hard enough. Why make it harder for the people you are presumably trying to help?

The word “allergy” was not originally and is not currently defined as being only an IgE reaction. A search on dictionary.com shows 10 definitions, none of which define "allergy" as being exclusively an IgE reaction. Below I copy the most comprehensive definition.

allergy (āl'er-jē) An abnormally high immunologic sensitivity to certain stimuli such as drugs, foods, environmental irritants, microorganisms, or physical conditions, such as temperature extremes.
These stimuli act as antigens, provoking an immunological response involving the release of inflammatory substances, such as histamine, in the body. Allergies may be innate or acquired in genetically predisposed individuals. Common symptoms include sneezing, itching, and skin rashes, though in some individuals symptoms can be severe. See also
anaphylactic shock.
American Psychological Association (APA):
allergy. (n.d.). The American Heritage® Science Dictionary. Retrieved December 13, 2007, from Dictionary.com website:
http://dictionary.reference.com/browse/allergy
Note that it says “an abnormally high immunologic sensitivity”, not “an abnormally high IgE sensitivity”.

On wikipedia.com, the history of the word “allergy” is explained:

The concept "allergy" was originally introduced in 1906 by the Viennese pediatrician Clemens von Pirquet, after noting that some of his patients were hypersensitive to normally innocuous entities such as dust, pollen, or certain foods.[2] Pirquet called this phenomenon "allergy" from the Greek words allos meaning "other" and ergon meaning "work".[3]Historically, all forms of hypersensitivity were classified as allergies, and all were thought to be caused by an improper activation of the immune system. Later, it became clear that several different disease mechanisms were implicated, with the common link to a disordered activation of the immune system. In 1963, a new classification scheme was designed by Philip Gell and Robin Coombs that described four types of hypersensitivity reactions, known as Type I to Type IV hypersensitivity.[4] With this new classification, the word "allergy" was restricted to only type I hypersensitivities (also called immediate hypersensitivity), which are characterized as rapidly developing reactions.
http://en.wikipedia.org/wiki/Allergy

Note that Dr. von Pirquet called the observed reactions of the immune system “allergy” without specifying that the term was only for IgE reactions. At the time immunoglobulins had not been discovered yet. The word continued to be used in this way for 57 years, from 1906 till 1963.

I was able to get a copy of the second edition (1968) of the Gell and Coombs book, Clinical Aspects of Immunology, from interlibrary loan. It does not say the word allergy should only be used for IgE reactions. I read all the sections about allergies, and it does not say this. At the time IgE had barely been discovered and it is called “reagin” through most of the book. This is what it does say in the Introductory Chapter on page xxiii:

Allergy, allergist, allergic reaction: MEANINGS: defined by von Pirquet who introduced the words, see Chapter 20 and Appendix A. USAGE: so varied and inconsistent at present that the words actively hinder understanding, but broadly equivalent to hypersensitivity, etc. BAD USAGE: we recommend a return to the use of von Pirquet as meaning broadly ‘altered in reactivity’.”
Appendix A is a translation of von Pirquet’s original article that identified and named allergy.

“The vaccinated person behaves towards vaccine lymph, the syphilitic towards the virus of syphilis, the tuberculosis patient towards tuberculin, the person injected with serum towards this serum, in a different manner from him who has not previously been in contact with such an agent. Yet he is not insensitive to it. We can only say of him that his power to react has undergone a change.

For this general concept of a changed reactivity I propose the term Allergy.”
Throughout the book the authors use the term “allergy” more broadly than any use it today, so they obviously did not wish to restrict the use of the word. They call auto-immune diseases “auto-allergic”, they refer to sensitized cells as “allergized”, and there are many other examples.

As my primary doctor pointed out, the term “non-IgE allergy” would also be useful to medical professionals as a reminder that the reaction is not IgE-mediated. The word can be adapted in many ways. Instead of saying “allergy” medical professionals can be more precise and clear by saying “IgE allergy” or “Type I allergy”. They could also say, for example, “T-cell allergy” or “Type IV allergy” and so on. These terms would be much clearer for everyone, including themselves, than the terms they currently use.

Everyone except medical professionals already use the term “allergy” in the way originally defined by von Pirquet and on dictionary.com. When I tell people I can’t eat certain foods, I say I have food allergies. This is much more clear than saying I have a hypersensitive immune reaction. In terms of normal conversation between lay people, it would be ridiculous to use any term except “allergy” to describe these reactions.

Even if the allergy/immunology establishment can’t bring themselves to use the term “non-IgE allergy”, they need to settle on one term that clearly describes the concept. Please, no more “non-allergic”!!!

I plan to continue pushing them to stop trying to change the meaning of the word and instead focus their energy on accepting and using information about non-IgE allergies to help their patients. Maybe if all of us patients do this, they will let go of their confusing and territorial ways and use the language the way the rest of us do, and maybe they’ll also accept and use the available information about non-IgE allergic reactions. :-)

References:
Clinical Aspects of Immunology, 2nd edition, edited by P.G.H. Gell and R.R.A. Coombs, 1968.
The Immune System by Peter Parham, 2000.
Food Allergies and Food Intolerance: The Complete Guide to their Identification and Treatment by Jonathan Brostoff, MD and Linda Gamlin, 2000.