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Are We Really as Allergic as We Think?

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We all know people who are allergic to something, whether it's the hay fever sufferer who sneezes every summer, or someone who has to omit some foodstuff from their diet because it doesn't agree with them.

There is a massive market in allergy treatment and management. One estimate put the US market alone at $9.6 billion. The antihistamine market was put at $4 billion in 2006, and corticosteroids also at around $4 billion. That's big money in anyone's book so there is a huge commercial interest in persuading us that we have allergies that need treatment.

A few years ago I was with a group of eight colleagues on a training course and at our table alone there was a coeliac, someone allergic to nuts, another to lactose, and one who complained of egg allergy. On the incidence statistics alone, I was incredibly lucky to be sat at that table: I figured the probability to be around 1 in 5500 that they would all appear in a sample of eight.

Clearly someone wasn't really allergic to what they thought they were. The coeliac, suffering from years of gut problems, had been diagnosed with gluten intolerance following a long series of hospital tests, but the others? They'd self-diagnosed, associating an upset stomach with a foodstuff that affects a lot of people.

We're very vulnerable to the suggestion that we are ill and need treatment. The worried well syndrome encourages people to become very conscious of the state of their health even to the extent of seeking treatment for non-existent illnesses. But clearly that's not the whole story. Certainly having a dietary condition is almost a chic fashion item, making the owner in some ways special. But that rather fickle cause aside, why do so many people think they are suffering from allergies?

The incidence of recorded allergy goes up and up year on year and that may well reflect people becoming more sensitive to chemicals in the environment, a growing weakness in immune responses, but how are they tested?

Sometimes of course, the patient simply believes some Woo merchant, someone untrained in clinical science who has simply checked their aura or measured their energy and pronounced some nonsensical diagnosis. That certainly accounts for a number of those claiming to be allergic. But others have undergone some kind of test at a clinic, typically a skin test in which it is lightly scratched so that an extract of the test foodstuff can cause a reaction. Sometimes the blood is tested for antibodies in what is called a RAST test.

But there is a problem with these tests, the problem of false positives. Around 50-60% of these tests are false positives. Now that can skew the results massively.

Let's see what happens when we look at some sample numbers. Suppose our test is pretty good, around 90% accurate. So 90% of those who test positive and are told they have the allergy, really do have it. The other 10% are told they don't have it, but do. Now let's suppose that the allergy affects 1 in 500 people so it's fairly uncommon, and let's suppose we test 10,000 people. Now we'll do the sums.

We know that of the 10,000 people in the sample, 20 of them have the allergy. Of those 20, 18 are told correctly that they have it, and the other two are told incorrectly that they don't.

Now what about the other 9980 other people who were tested? Well, 10% of them were incorrectly told that they had they allergy and that's a total of 998 people. The remaining 8982 are told correctly that they don't have the allergy.

Now let's check the results:
Total told they have the allergy, 1016.
Total told they don't have the allergy, 8984

Number who actually have the allergy? 20

So the probability that someone who is told after the test that they have the allergy really does have the allergy is actually around 2%. But if you're told you don't have it, the probability that that's right is around 90%. So you can be reasonably confident of a negative result but not of a positive result.

Now that was with a test which was assumed to be 90% reliable. But we know the reliability of the scratch test and the blood test for allergies is much much lower with false positives reaching 50-60%.

The problem with these tests is that they crucially depend on the real incidence of the allergy and if the assumed figure for incidence is higher, then that leads to claims that the test is more effective. But it's a circular argument if the scratch or RAST test is used to assess incidence itself.

So maybe, just maybe, we're responding to cultural pressure to self-medicate our self-diagnosed allergy symptoms. It may well be that the incidence of allergy is on the increase – it wouldn't be surprising given the number of synthetic chemicals in our world and the biological reactions some of them cause. But the growth in self-diagnosed allergies, although it's music to the ears of the $10 billion market, may well be vastly outstripping the real incidence.

Maybe we need to stop and think before jumping to the conclusion that we too are allergic to something.

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About Bob Lloyd

  • Jennifer

    Thanks for your blog. Now you make it even harder for those of us who have had a diagnosed food allergy to have anyone take it seriously. So we pretty much have to document every single reaction, go through our clinical history, quote skin prick and RAST tests and any related reactions before anyone will believe us. And when we do this, you will turn around and criticise us for bleating on about our allergies. At the moment, food allergy sufferers just can’t win.
    Yet if you have diabetes, you don’t have to do any justification.

  • Jennifer, I’m sorry that you feel this is about justification for claiming an allergy rather than accurately identifying if it is the case. As I said in the article, the incidence of people saying they have an allergy is greatly more than those who have identified allergies.

    It’s an unfortunate fact that where the incidence of any ailment is low, and the accuracy of the test is not exceptionally high, the incidence of false positives often invalidates the conclusion. We can’t do anything about that fact except try to develop tests with very high accuracy levels.

    What I am arguing is that having someone say you are allergic to something may well be less certain than they imply especially if they are relying on a scratch test. If it is one of the varieties of Woo such as Chinese medicine, Ayurvedic medicine, Reiki or some other mystical therapy, their diagnosis will be almost certainly guesswork.

    In the case of diabetes, there are exceptionally reliable tests. For example the Hb1a blood test measures long term sugar levels, and a high reading is a reliable indication of problems maintaining correct blood sugar levels over time. We can hope that there will eventually be allergy tests with a similar level of accuracy. If or when that happens, allergies will be identified much more specifically.

    That will almost certainly mean that a large number of self-diagnosed allergics will find that they are not in fact allergic to the substances they claim.

    The present situation is one where many people are attributing their ailments to allergies when they are quite likely not to have an allergy at all. If the ailments are such as to need treatment, it is really important to identify accurately what the cause is, rather than have them believe that avoiding certain foods is the answer. For people who are genuinely allergic to a specific foodstuff, avoidance may well be an adequate treatment, but for those wrongly diagnosed, they are interfering with their diet for no real benefit. I have met many allergics who continue to compalain of the same symptoms despite their dietary changes.

    I am not saying that they are not suffering from some other condition that might need treatment. Simply that in many cases it won’t be an allergy. There’s a large pharma industry benefiting from our willingness to self-diagnose and get it wrong.

  • “The coeliac, suffering from years of gut problems, had been diagnosed with gluten intolerance following a long series of hospital tests”

    Coeliac disease or gluten intolerance; which one? The two are completely different:

    “Coeliac disease (pronounced see-liac) is not an allergy or simple food intolerance.

    In fact it’s an autoimmune disease, where the body’s immune system attacks its own tissues.

    In people with coeliac disease this immune reaction is triggered by gluten, a collective name for a type of protein found in the cereals wheat, rye and barley. A few people are also sensitive to oats.

    In coeliac disease, eating gluten causes the lining of the gut (small bowel) to become damaged and may affect other parts of the body.

    What are the symptoms?

    The symptoms of coeliac disease vary from person to person and can range from very mild to severe. Not all effects of coeliac disease are related to the gut.”

    From the Coeliac Society

    In short, gluten intolerance does not cause a person’s immune system to damage their own gut, while Coeliac disease does.

  • In fact, the coeliac does have an intolerance problem with glutin-type proteins because it is the metabolism of gliadin (a glycoprotein found in wheat and other cereals) which causes the enzyme tissue transglutaminase to modify the protein which creates the immune reaction. Glutins are composites of gliadins and glutinin – it’s the gliadin part that causes the problem for coeliacs.

    In the UK and I believe also in the US, coeliacs are routinely referred to as glutin intolerant because they react to gliadin, and the only known treatment is a glutin-free diet.

    In fact wiki refers to it as a glutin intolerance as well. It’s a common description of the condition.

  • Wiki is hardly the best source of information. Do they check the medical qualifications of their writers?

    The NHS is a better source IMHO:
    Food allergy and food intolerance

    Allergy: Produces acute distinctive symptoms, usually within seconds or minutes. In extreme cases, can be life-threatening. Isn’t dependent on the amount eaten. Even a tiny trace amount of the food can cause a reaction. The culprit food is never craved. Can be diagnosed by an expert using several tests and a medical history.

    Intolerance: Produces delayed chronic symptoms, which mainly involve the digestive system. Is never directly life-threatening. Is usually dependent on the amount eaten. A reasonable portion of the food is needed to cause a reaction. The culprit food may be craved. Is difficult to diagnose. Only a few reliable tests are available.”

  • Bob, one thing you skip is that there _is_ a reliable way to ensure that the RAST allergy diagnosis is correct. (My web link here explains the nuts & bolts.)

    A 2-week food elimination trial is the next step that almost all medical doctors (and Woo practitioners) will recommend.

    You go off the “suspect” food for 2 weeks, and at the end of that time period, you eat it. If nothing happens, you can eat it without problems thenceforth. If something does happen – you get diarrhea, a skin rash, etc – then you know you have some sort of reaction to the food. Even self-diagnosers can ensure their allergy/intolerance with this test.

    The other thing the ill person can do is check to see if the actual response to the food is something they can live with from time to time if they “cheat”. (e.g. some people will live with pimples for a taste of chocolate cake, whereas someone with gluten intolerance knows that the repercussions are far greater for themselves.)

    Another blind spot in your article are non-allergic conditions that could also cause an individual to have to stay away from certain foods.

    “Allergy” is a very specific term that signifies a histamine response in the blood stream. Often, people with non-allergic conditions including an auto-immune respose like celiac or people with insufficient digestive enzymes to properly break down certain foods (often referred to as an intolerance) will SAY they are allergic because it is the accepted lay-man’s term for “I can’t eat that, don’t give it to me.”

    Clearly, this is a hot-button topic, and very easy to misunderstand or mis-state.

    Personally, I believe we all have the right to avoid foods that upset our systems just as much as we have the right to avoid foods that we just plain don’t like. And I do resent having to give people a medical work-up every time I order a meal at a restaurant that they don’t see as “normal”.

  • I’m not really sure what you’re claiming. Do you think that coeliac disease is really not an intolerance to the gluten gliadin? That the enzyme does not modify the protein causing the immune response? I really don’t think there’s any doubt about the aetiology of the condition, nor any shortage of very solid medical information. Check out Mario Cassar’s site for example, and his credentials if you are unsure of the information.

    If you are claiming that coeliac disease is more serious than allergies and intolerance, the fact is that some allergic reactions can be fatal. But surely it’s not about claiming the most serious illness?

    As for the NHS information, they too say that coeliac disease is gluten intolerance. See the introduction here and you’ll see that they describe exactly the same cause as I posted above.

  • Atlanta, I think that’s absolutely right – that the test for coeliac disease is precisely the kind of exhaustive elimination diet with controlled reintroduction over a period of time of specific foodstuffs. It has to be tightly controlled so the patient has to know precisely what is in their food. Even a small amount of gluten may well remain even when the selected foodstuffs are avoided, which makes even the elimination diet difficult to control.

    The sheer difficulty of controlling the contents of our food makes an elimination diet a long and painstaking process. But that’s what is required to identify gluten intolerance definitively.

    When people decide to try dropping a particular foodstuff, unless it’s part of a very carefully controlled trial (with known composition of all the food they eat), they are unlikely to be following a real elimination test. So sure, people may decide that they feel better missing out a certain foodstuff, but that’s obviously not the same as diagnosing either an allergy or an intolerance. It might give the impression of self-diagnosis, but there will be many other factors influencing it, including the placebo effect.

    It is a touchy subject, because many people are genuinely convinced they are allergic to something, far more than is evidenced by the real incidence. But there is so much statistical doubt about the tests and diagnoses, and especially over the extent of self-diagnosis, that many people are simply convincing themselves they have some allergy or intolerance.

    Incidentally, histamines actually perform an important biochemical role in potassium metabolism so routine suppression of histamines is of course not an answer.

  • My method worked better:

    get stung by bee, swell to 150% my size
    get tested, said false
    get stung again, lose conscinous and rushed to hospital
    get tested, positive
    pretty sure that i am allergic to stinging insects

    then, with crab:
    eat some, love it, fine
    repeat 20 years
    21st year, eat it, get vilontly ill, assume food poisoning
    try again, get sick, cant feel body, tounge swells, can barely gasp for air, hospital
    get checked, positive
    i am pretty sure

    frankly, had I had tests, i could have avoided the problem had they said yes.

  • Robert’s method:

    get stung by bee, swell to 150% my size
    get tested, said false
    get stung again

    Stop. Hang on a minute. You went back to the bees because you’d tested negative??

    Surely it is wiser to avoid bees because they sting, not because one might be allergic to them?


  • Robert’s bee sting test makes an excellent point. So, does his intermittent shellfish allergy (which I also have–resulting in hives every ten, five or three years). This never prevents me from eating the delectible creatures. If anything would, it would be that they look like bugs. Ick!

    Good luck with allergy tests.

  • Judith Poser

    It was reading comments like yours that prevented me from being tested earlier for food ‘allergies’. I did not want to be a malingerer or be perceived as making a fussy lifestyle choice. In fact I had coeliac disease and became incredibly unwell. When I had an endoscopy I hesitantly asked the doctor if I could be allergic to gluten. He told me I had been reading too many women’s magaznes….. It is thoughtless articles such as yours that can lead to a lot of misery and prevent diagnosis, not to mention much cynicism afterward from people who think you are being neurotic. Please be careful what you say to amuse or for personal gain, and think of the people you may harm on the way.

  • Judith, the whole point of the article is to raise awareness that identifying allergic conditions requires controlled tests which need to be highly accurate when testing for uncommon ailments. The earlier posts comment also on their inaccuracy.

    Having people declaring allergy on the basis of inaccurate tests raises anxiety and leads to many people thinking they are allergic to something when they are probably not. It’s important to understand the accuracy of the tests, and the consequences of false positives. As I said in the article, even a test that claims 90% success, can result in a very low likelihood that a postive test is correct. That’s an important point to understand. Identifying allergies is not just a simple scratch test.

    I am sorry to hear you suffer from coeliac disease but glad that it was tested and identified. The cause is very well-established and it really is an immune reaction to the metabolic products from gliadin, a gluten component, which is why it is called a gluten intolerance. You can find lots of detailed information about this on PubMed if you want to follow up the research in the public domain.

    Of course there are some neurotic people who claim illnesses for their own psychological reasons, but there are very many more who genuinely believe they are allergic when the evidence is at best shakey. It is important for all of us to be thoughtful when weighing up such evidence because it affects the quality of our lives.

    Of course people who think they are suffering from an allergy should get it checked out, but they should also be aware of the question of false positives in the tests, and the need for controlled testing rather than informal self-diagnosis.

  • @10 no, it just meant that i was still removing the nests from the house. That is no longer the case

    @11 it isn’t intermittent, just didn’t develop until then (a little earlier than the family’s normal development of them (it is genetic, apparently))