In an attempt to stop the hijack of this thread I’m posting here.
I have long been taught that a true allergen must be an antigen that produces a type I hypersensitivity response. Over the years, many people have tried to assert allergies to things like cigarette smoke, sulfites and other things that (by my understanding) can’t produce a histamine-releasing reaction.
Mangetout, in the above mentioned thread, is contending that a) “Allergens don’t have to be protein-based” and b) and his “wife is severely allergic to SO2”
His cite states that “Some people (but not many) have positive skin allergy tests to sulfites indicating true (IgE-mediated) allergy.” Other pages here and here also suggest that a skin test for sulfites is possible. However, I can’t seem to find any reliable medical data on how such a reaction could occur.
So, now begins the debate…
What is an allergen? Can someone technically be allergic to a non-antigen?
probably not a medical definition - but an allergen is anything that invokes a ‘response’ - it may be that SO2 is more appropriately called an ‘irritant’ as opposed to ‘allergan’ - yet the symptoms may be the same.
The linked document appears to be stating that some people are genuinely allergic to sulphur compounds (i.e. they stimulate an immune response involving histamines, inflammation, etc), however, the more commonly experienced effect is irritation (which is often colloquially referred to as ‘allergy’).
Obviously this next statement is not a cite, but the reason I know about this is that my wife is severely allergic to sulphites and SO2 - on several occasions in the past, she has had Anaphylactic reactions following consumption of commercial bottled wine/cider (containing sulphites) or packaged dried fruit (containing SO2 as a preservative) - requiring emergency hospitalisation for intubation and treatment with antihistamines and steroids.
She has also experienced numerous less severe cases (for example, when exposed only to the gas and spray emitting from an opened bottle of sparkling wine), or after opening a bag of dried fruit without consuming any, the onset is slow enough that she can catch it early and self-medicate with antihistamine tablets or liquid. This usually prevents the worst symptoms (i.e. the worst of the respiratory difficulties), but still knocks her off her feet for hours.
FWIW, my armchair theory about this is that the SO2 is probably denaturing proteins in her body, and these denatured proteins are the subsequent trigger for the immune response.
Also, only because it’s bound to come up - there is something called Allergic Contact Dermatitis, which is often triggered by metals, however, I think that’s a different enough class of allergic response that we can leave it aside completely.
First off, 100%, not all “responses” are allergies. Not “everything that makes you sick, but doesn’t make most other people sick,” is an allergen. For example, I get migraines from mussels but I am not allergic to them. It is a different sort of food intolerance. Celiac disease similarly is not an allergy to gluten.
Allergies are specific sorts of immune mediated hypersensitivity reactions. A decent review is here (pdf).
The reactions can be IgE to histamine mediated, Type I, Immediate type; or mediated by IgG and IgM, cytotoxic, Type II, which is caused by small molecules binding to proteins of your own body and modifying them, such that they are now identified as non-self (haptens, common for drug reactions, which are often not proteins); or another sort of IgG and IgM one, serum sickness; or the delayed reaction mediated by T cells, Type IV, which is the sort caused by poison ivy.
In each case the allergen is that which triggers the reaction of one of those classes. And to re-emphasize, only one of those classes of allergic responses is IgE to histamine mediated.
Cigarette smoke contains somethng like 4000 or so compounds, from plant proteins to a plethora of poisons. Some of the reaction to smoke is physical irritation causing inflamation; some is via allergic mechanisms. It is certainly possible to have an IgE mediated allergic reaction to one of those antigens and possible to have a smaller compound trigger a non-Type I hypersensitivity reaction. Mostly though the researched role of tobacco smoke in allergies is its ability to act as an adjuvant making reactions to other allergy antigens much greater. See here for one small example.
Clearly sulfite allergies exist. I think though the question for cigarette smoke is more sulfur dioxide which cause allergies more as the potentiator of allergens. It does not act alone. In that sense in most cases it is not functioning as an allergen even though it provokes/amplifies an allergic response to something that is an allergen.
In any case, I think the underlying statement (the one I originally challenged, quoted below) is false, on two levels.
It appears there are mechanisms by which exposure to smoke or other non-protein-based substances can result in an allergic outbreak.
(Off topic for this thread, but not the hijack to the other one) Regardless of the precise mechanism, or even the precise type of reaction, responding to the question “may I expose you to chemical X?” with “Please don’t - I’m allergic” is still a sensible and reasonable response.
The waiter does not need to understand or care that your aversity to shellfish is actually because of an intolerance. The person offering you a glass of sulphited wine does not need to know or care that the sulphite releases Sulphur Dioxide, which is then a factor in a chain of events, leading to anaphylaxis. “No thanks - I’m allergic to it” is probably the right thing to say.
In that vein, my wife and I went out to eat at one of those pre fixe meal places, chef’s choice grand degustation, and the waiter asked if either of us had any food allergies. My wife jumped in and said I was allergic to mussels and I corrected her, saying I am not allergic, they cause migraines but it is not an allergy. Her response was simply: “A normal person would say they were allergic.”
DSeid, thank you for the detailed response. I’m still unclear about a few things though.
According to Immunology, “the term allergen refers specifically to nonparasitic antigens capable of stimulating type one hypersensitive responses in allergic individuals.” By this definition type 2-4 hypersensitivities, as far as I can tell, are excluded as being considered allergies and simply classified as hypersensitivities.
Haptens are an odd classification, mostly because they must be attached to a protein to illicit any reaction. This is still congruent with my original statement.
Though I am willing to admit it’s possible, I haven’t been able to find any evidence to support that an IgE response has ever been recorded. Frankly, with all of the work and study done on cigarettes, you would think that we could find at least one study that bears this out if it were possible.
Agreed.
I’m still having some trouble with this. I can only view the abstract, so perhaps I’m missing an important part of the article. I still don’t understand the mechanism for how a sulfite can produce an IgE response.
According to definitions here, here and here any reaction from a sulfite would still be considered a hypersensitivity.
No, this hasn’t been established. As I stated above, haptens must be attached to a protein to illicit any response. And DSeid’s response only speculated that cigarette smoke may contain proteins which could *possibly *produce an allergic response.
Thus far, the only thing really in contention is sulfites causing an IgE response and being a true allergy. To this point, I have to admit there’s really not enough data either way. I haven’t been able to find a medical study or proof that sulfites cause an IgE response, but I can’t rule it out either. Some cites, such as yours, suggest it’s possible, but there’s no explanation for the mechanism on how which makes me a little suspect.
My statement in the other thread was specifically in response to a medical professional who was stating she may use a (non-existent) cigarette smoke allergy as an excuse to keep friends at a party from smoking around her. An excuse made even more dubious by the fact that she is a former smoker.
I never suggested that people should never use the term allergy for their food server or other similar situations out of convenience. I just don’t think lying about a fake allergy for your friends and acquaintances is the way to go, especially when it’s (nearly) impossible for it to be true.
According to the middle one of those links, an allergy is a type of hypersensitivity.
Nobody is saying that all sulphite sensitivity should be called allergy. Several of these cites (albeit that we can only see the abstracts*) are talking about two classes of phenomenon - a common sensistivity, and a rare allergy.
*Is it normal to suspect abstracts of misrepresenting the whole paper?
Most of what I read does not limit “allergy” to Type I Hypersensitivity but even accepting that definition it is still true that there are mechanisms by which a non-protein substance can provoke an allergic response. A hapten binding to a self protein which then triggers an allergic cascade is still the non-protein provoking the response. Tobacco smoke provoking TH2 responses and by way of functioning as an extremely effective adjuvant allowing an allergic reaction to occur is still its provoking the allergic response. Moreover, whether or not an IgE response to the proteins in tobacco smoke has been ever documented is immaterial to the statement that such “can” occur. Finally such have been documented. http://www.modernmedicine.com/modern-medicine/news/modernmedicine/welcome-modernmedicine/tobacco-may-trigger-specific-allergic-i-0
Correct. An allergy is a type of hypersensitivity, but not all hypersensitivities are allergies.
I agree with you.
I don’t necessarily suspect the abstract is misrepresenting the whole paper, but for example DSeid’s cite states"the mechanisms underlying sulphite sensitivity remain unclear."
And your original cite doesn’t reference any medical studies or scientific data just states that “some people” have an IgE reaction. I haven’t been able to find anything else reliable that supports this claim.
As I stated in my previous post, I’m willing to admit it’s possible and I can’t rule it out. However, I’m having trouble finding anything to support it.
spelling with the f has been preferred since 1990. the ph spelling may still be used in British empire countries. the change is well within the life and the educated life (since high school level sciences) of many people.
i would say until a bunch of people die that it is old fashioned.
