Definition of ‘Allergy’

“I don’t care if you call it an allergy or a sensitivity. I don’t care which immunoglobulin set it off. All I know is that I’m not getting enough air!”

Ahh, the power of language. I said that when I was in the ER, and having an anaphylactic reaction. The nurse chose that moment to debate whether a ‘mast cell degranulation’ was a ‘sensitivity’ or an ‘allergy.’ While I find that type of intellectual conversation fascinating…if I’m on the express train to shock, I don’t care what you call it; just give me the epinephrine!

Consider the following statements:

“I’m allergic to the smell of peanut butter.”

“I’m allergic to walnuts and pecans, but almonds and hazelnuts are fine.”

“I’m allergic to grapes. I can eat a few grapes every three days.”

“She’s terribly allergic to blueberries. Gives her ‘allergy poop’ for days.”

“I used to be allergic to peanuts, but I’m not anymore.”

“The tiniest trace of cows milk and her excema gets awful.”

“I’m allergic to pineapple. My  dermatographia always flares when I eat it.”

These statements are either ‘possible’ or ‘impossible’ depending on your definition of allergy.

The ‘old’ definition af allergy is based on what we call the ‘IgE’ allergy pathway. Many physicians still practicing learned in school that an allergy was limited to an IgE mediated reaction to an allergen inducing protein. (IgE being one of the immunoglobulins. They are one type of cell the cells that set off ‘intruder alerts’.). This definition is very narrow, and can’t be determined clinically. Some blood and urine tests can hint at different pathways, but if you are in an ER in full anaphylaxis, that isn’t practical, or particularly helpful (yet?).

I’m not particularily fussed about whether I call it an allergy, a sensitivity, a mast cell degranulation, just as long as the person I’m talking to is using a matching definition. The biggest issue that I have come up against is that a narrow definition ‘dismisses’ other reactions, minimizing them as somehow less ‘valid’ or ‘important’. I have had many allergies dismissed as not being ‘true allergies’. (I have found that I use the word ‘reaction’ with new people and physicians. It seems to be universally accepted).

I think I can tell when my reaction is an IgE, IgG or mast cell ‘overload’ reaction, but describing it, let alone testing for it is another thing altogether. The symptoms are the same, it’s a matter of degree, speed, order, intensity, etc. that tells me; it’s subjective and unique for everybody. I can go into anaphylaxis from IgG reactions, IgE reactions and mast cell degranulation. The symptoms overlap and intermingle, and one type of reaction can set off another, due to feedback loops in our immune system. This is not to say that figuring out which pathways are involved isn’t useful. It can currently be helpful in preventing reactions (for example, there is a medication called Xolair that targets IgE receptors. If your IgE pathway doesn’t have any problems, it’s not going to help…). There are some lab tests that point to one pathway or another, but they are notoriously difficult to ‘catch’, and researchers are a long way from figuring out all the allergic pathways (and their feedback loops). Once they figure that out, there’s the challenge of being able to determine which ones are involved at any given moment, and then tailoring treatments based on that information. Currently, in an emergency situation, it doesn’t help. (I hope one day it will, but not yet).

There are multiple definitions used currently- none of them specify which type of immunoglobulin is involved, or are as narrow as that old definition. If you would like a full historical breakdown, this article at Mast outlines it all.

For the purposes of this site, I’m going to try to use a definition that is definitely at the ‘broader’ end of the spectrum. I can’t say which current definition is ‘perfect’. Much more critical is that the statements above are all true for me or my child, so my definition has to reflect that. I don’t think any one particular definition is ‘better’ or ‘worse’. As long as we all know which definition we are using, that’s the key. If I am having a conversation with a physician, and we are using different definitions, it will lead to confusion, misunderstandings and can have far-reaching consequences.

This is the definition of “Allergy’ that I intend to us as a starting point.

A maladaptive response to an internal or external stimuli that causes an immunological reaction involving mast cell activation.

Here are the premises underlying that definition

1. There has to be a trigger. (Ideopathic anaphylaxis deserves a post in and of itself. I beleive that all ana has a trigger, but sometimes figuring out what it is is almost impossible, and many physicians aren’t willing to accept all triggers.)

2. It has to involve the immune system, and mast cells in particular.

3. It’s not good for you. Reacting with a little bump to a mosquito bite is ‘adaptive’, it tells you that there are insects biting you, potentially carrying pathogens. So, you cover up. If a mosquito bite causes throat swelling, that’s a problem…it’s maladaptive.

4. Reactions can be triggered by internal states (e.g. dehydration, startling, fatigue, exercise, stress), external factors (temperature, UV light, vibration, scent, etc.), and ‘allergens’ (what we typically think of- dairy, soy, pollen, cats, etc.) Any of those triggers can contribute to, or even set off, a reaction. A protein molecule is not required.

5. Allergies are not ‘binary’; they dont act like on/off switch. It’s a mater of degree,  and how allergic I am to something changes from moment to moment, and from year to year. As with most things, it’s on a spectrum, the severity based on a multitude of factors.

I realize that this is a very broad definition, based on premises that some may not agree with. The definition is far from ‘perfect’, as language is highly imperfect. The nmore specific you want it to be, the more words you need. If it was easy for humans to use words to define concepts, we wouldn’t need lawyers or philosophers… I’m certain that my definition will shift next several years, and hope that a common definition is found that works for everyone. In the meantime, I’m using the above definition as my ‘starting point’.

Are you still here? Start a discussion!