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When is a Food Allergy Test NOT a Food Allergy Test?

Jason is now 15. He is taking AP calculus at Desert Vista High School, plays La Cross after school, is getting his driver’s permit next week, and plans to go to college and study electrical engineering after graduation. He is smart, tall for his age, and spends a little too much time playing video games.

He is also deathly afraid of peanuts.

He is afraid, in spite of the fact that he has never eaten a peanut. He has never enjoyed a Snickers bar, Reese’s Cup, or Kung Pao Chicken, and has certainly never eaten a peanut butter and jelly sandwich for lunch.

And yet, as long as he can remember, his parents have sternly warned him to stay away from peanuts.   He was not allowed to eat lunch with his friend’s at school because he had to eat at a special “peanut free” table and could not have snacks brought by other parents to baseball practice because they might be “contaminated” with peanut.

His parents have had to buy three sets of Epi Pens each year to keep at school, at home, and at his grandparents home, to be used in case he had a severe allergic reaction after eating peanut by mistake. This year his family spent more than a thousand dollars on the Epi Pens.

All in all, Jason’s life and the life of his family has been complicated by the serious threat of peanut allergy. And yet, Jason is not allergic to peanut.

The problem began when Jason was just turning two. He was spending the day at his grandparent’s house and developed a rash on his cheeks and vomited.   His parents became concerned that he may have had an allergic reaction to something he ate and so took him to his pediatrician who decided to run a food allergy panel just to be sure.

The test came back positive for peanut. The pediatrician suggested that it might be best for Jason to avoid peanuts since if was unclear if he may have eaten something that contained peanut at his grandparent’s house.   His parents read a story about a child with severe peanut allergy who died after being kissed by someone who had eaten a peanut and so requested an Epi Pen to keep on hand. All family members, friends, and teachers, were instructed on the importance of strict peanut avoidance when around Jason and on the use of an Epi Pen.

I saw Jason for first time six months ago.   His parents needed a refill of the Epic Pens and since his pediatrician was no longer practicing, they decided to make an appointment with an allergist.

After talking with Jason and his mother, it was clear that Jason did have allergies. He sneezed frequently, complained of stuffy nose and itchy eyes during the spring and fall, particularly while playing La Cross, and on occasion had wheezing and chest tightness after spending time around a friend’s cat.   Mom was not concerned about these symptoms, lot’s of people had them, but she with very concerned about his severe peanut allergy.

Because of his history, allergy testing to pollen, cat dander, and peanut was completed. The results showed very strong reactivity to grass, tree, and weed pollen as well as to cat dander. The skin test to peanut was also mildly positive.

How do we interpret these results? Most importantly, is Jason allergic to peanut?

To begin we rely on three sources of information to help us make a diagnosis of allergy: the patient’s history, laboratory tests, and a food challenge.

In Jason’s case, the history is not very strong for peanut allergy. In fact, it is not clear if he has ever been exposed to peanut.

What about the positive blood test and skin test for peanut allergy?

Both tests rely on the detection of a specific antibody produced by the body that reacts with peanut. When we find these antibodies, called IgE or immunoglobulin E, we can say that the patient shows sensitization to the food being tested. Both the blood test run when Jason was two and the recent skin test are technically not allergy tests, but tests for sensitization.

This distinction in terminology is important because many people have sensitization to a food (based on skin or blood tests) that they have eaten their entire lives without problems. Since food allergy by definition is adverse symptoms caused by exposure to a food that a patient is sensitized to, then without symptoms, there is no allergy.

If we define a perfect food allergy test as being reactive or positive in 100% of patients who have true allergy to the food and non-reactive or negative in 100% of patients who are tolerant of the food, meaning it is safe for them to eat it, then conventional food allergy testing is not very good. In fact, conventional food allergy testing has an approximately 50% false positive rate: Half of the patents that test positive to a food on these allergy tests are NOT allergic to the food. The test’s ability to rule out allergy is better, by some estimates more than 90%: There is less than a 10% chance that a patient with a negative test to a food will have an allergic reaction if they eat the food.

When we say that conventional allergy tests for peanut allergy have a 50% false positive rate we do not mean the test result is an error or mistake. The test accurately detects allergic or IgE antibodies to peanut. But as was mentioned, the presence of these antibodies does not always cause problems when the patient eats peanut and therefore is considered a falsely positive test for food allergy.

To understanding WHY we can have allergic antibodies to a food that we tolerate it is helpful to understand a few things about proteins. You can find a brief introduction to proteins here.

Peanuts, as well as most other foods, contain multiple proteins. The proteins in peanut are given numbered names beginning with Ara h (from the scientific name for peanut Arachis hypogaea). The peanut proteins Ara h1, Ara h2, Ara h3, Ara h6, Ara h8, and Ara h9 have been detected and allergic IgE antibodies have been found that react with each of these proteins.

Some of these peanut proteins, such as Ara h8, are very similar to proteins found in pollen produced by allergenic plants. In fact, if a patient is allergic to birch tree pollen, the anti-birch tree IgE antibodies they produce are likely to react with the Ara h8 protein in peanut. Patients with allergic antibodies to Ara h8 alone rarely have significant peanut allergy and yet will have a positive skin or blood test to peanut. One study showed that 79% of patients who had allergies to pollen reacted positively to peanut on an allergy test but were tolerant of peanut.

Other studies have shown that patients with high levels of allergic antibodies to the Ara h2 protein in peanut are more likely to have true peanut allergy. These observations have led to the development of component allergy tests were a patients blood can be tested for allergic antibodies to a specific food protein, not just the whole food.

Component testing for peanut allergy does show improved diagnostic accuracy compared with conventional blood tests, although it continues to have a high false positive rate and unfortunately can also be negative in patients who have true peanut allergy.

Component allergy testing for peanut was ordered for Jason and the results showed positive to Ara h8 only suggesting that the positive result on the skin test and earlier blood test occurred because of his strong sensitivity to pollen.

The results were discussed with Jason’s parents who asked if there was any other test that might be used to confirm that he is not allergic to peanut.

In fact, the most reliable and considered to be the gold standard for making a diagnosis of food allergy, is the double-blind, placebo-controlled food challenge. In this test, the patient is given a sample of the test food as well as a sample of a similar, non-allergic food as a placebo. Double blinded means that the doctor and technicians conducting the challenge as well as the patient, do not know which is the real test food and which is the placebo. The test is considered positive if the patient shows obvious signs of a reaction after eating the test food but not after eating the placebo.

There are a number of problems with the double-blind, placebo-controlled food challenge: It is difficult to perform, requiring significant time and recourses; A patient can have a severe allergic reaction to the food and therefore the study must conducted by trained personal in a setting that is capable of handling a severe emergency; and it is not always possible to find a suitable food to serve as a placebo.

Because a food challenge carries the very real risk of a severe allergic reaction it is rarely done if either the history or laboratory tests strongly suggest allergy. Open challenges to a food conducted in the allergist office is considered to be an alternative to a blinded, placebo-controlled challenger if the likelihood of significant allergy is considered to be very low based on history and previous tests.

Because of the weak history for peanut allergy and the results of component allergy testing, a peanut challenge in the office was offered to Jason and his parents.

When the food challenge was discussed with Jason he became very anxious and said that he did not see any reason to do it since he has done well staying away from peanut his whole life. He said he felt sick just thinking about it.

Hopefully, Jason’s fear of peanut allergy will subside with time and education and he will someday be able to enjoy a peanut butter and jelly sandwich or Snickers Bar.  And hopefully, improved testing methods as well as better understanding of food allergy will make such cases of unnecessary fear and anxiety over something to be enjoyed a thing of the past.

Brian Millhollon, MD

 

 

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Food Allergy for Beginners: Sugars

What is a Sugar?

Sugar is one those loaded words that can have a variety of  meanings.  For example sugar can mean sucrose, the white granules you put in your coffee, or it can refer to the level of glucose in your blood, as in: “I need to up my insulin because my blood sugar is sky high after putting all that sugar in my coffee”.

Sugar can also refer to carbohydrates (“carbs”), one of the three categories of chemicals, along with fats and proteins, which make up the food we eat.

Carbohydrates can be single molecules or joined together to form large chains.  Single molecules are called monosaccarides and include glucose, galactose and fructose. Any two of these simple sugars combined are called disaccharides. For example, sucrose (table sugar) is a disaccharide combing the two simple sugars glucose and fructose. Lactose is a disaccharide containing glucose and galactose. Polysaccharides are long chains of monosaccharide joined together and are used in plants and animals for structure and storage. Sugar is stored as starch in plants and as glycogen in animals.

Monosaccaride - glucose

Monosaccharide – glucose

Disaccharide Sucrose

Disaccharide Sucrose

Polysaccharide

Polysaccharide Starch

Sugars can combine with proteins to form glycoproteins and with fats to form glycolipids.

It’s All About Glucose

Glucose is our body’s primary source of energy and also the primary product of photosynthesis, the process in plants that turns sunlight into food.  Most of the carbohydrates that we eat are converted to glucose during digestion. We crave sweet things because they usually contain lots of simple sugars that require very little or no work to convert to glucose. Most of the cells in our body can run on either glucose, fats, or proteins but the brain needs glucose to work.Glucose metabolism

Can You Be Allergic to Sugar?

The short answer is no. Simple sugars and disaccharides such as sucrose and lactose are not allergens and cannot cause true allergic reactions.

However, people have become allergic to glycoproteins, sugars combined with proteins. An example of this is allergy to galactose-alpha-1,3-galactose, also know as alpha-gal.   Alpha-gal is a common glycoprotein found on all animal cells except humans and primates and those sensitized can have allergic reactions to a variety of meats including beef, pork, and lamb.   Interestingly, a large number of alpha-gal allergic patients developed symptoms after being bitten by a tick, particularly the lone star tick found in the Southern and Eastern United States. Skin testing to meat and a blood test for allergic antibodies to alpha-gal can make the diagnosis.

Lactose Intolerance

Although sugars rarely cause true allergic reactions, they are a common cause of food intolerance. Because the cells in our body can only use glucose for fuel, all complex sugars (disaccharides and polysaccharides) have to be chopped-up or digested to make the glucose available. To do this, we produce enzymes that make the process of digesting the complex sugars possible.   Many of these enzymes are specific for a particular type of sugar. For example lactase is the enzyme that facilitates the break down of cows milk sugar (lactose) to yield glucose and galactose that is then easily absorbed into circulation to be used as fuel.

Without lactase the milk sugar passes intact into the colon where it provides nutrition for colonies of fermenting bacteria. These bacteria feed on the sugar and as a by-product, produce a large amount of methane gas and fluid retention causing intestinal bloating, cramping, and gas.   Treatment is avoidance of all mammalian milk and/or taking supplemental lactase (Lactaid) whenever milk products are consumed.

In summary, true allergic reactions to carbohydrates are rare while food intolerance, such as lactose intolerance, are more common.  Other problems associated with sugar (i.e., how to say,  “No thank you” to that cheese cake) is an important topic, although – except as a fellow victim- a bit out of my area of expertise.

Brian Millhollon, MD

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Food Allergy for Beginners: Fats and Oils

As discussed in the previous article (Food Allergy for Beginners: Proteins), primarily it is protein in foods that causes the majority of allergic food reactions. Our diet also contains fat (oils) carbohydrates (sugars), and minerals but these rarely cause true allergic reactions.   This is an important point because many oils, such as peanut oil, are made from very allergenic nuts or seeds.

Is peanut oil safe to eat if you have a peanut allergy?

The answer to this question depends on the type of processing used to extract the oil.

Most vegetable oils used for cooking are produced using an extensive multistep mechanical and chemical process that begins by heating and crushing the seed or nut.   The oil is then extracted using the chemical hexane. Additional steps may include adding acids and steam distillation. The final product contains so little protein that the FDA does not require oils processed this way to be listed as a potential cause of allergic reactions.

Chick-fil-a, a fast food chicken chain, uses peanut oil and posts the following information about food allergies:

     “Chick-fil-A(r) cooks in 100% refined peanut oil. According to the FDA, highly refined oils such as highly refined soybean and peanut oil are not considered major food           allergens and therefore are not listed here”

Oils may also be extracted from nuts and seeds using only mechanical press without heat or chemicals.   This method produces much smaller amounts of oil but the oil produced retains more of the natural flavor and also may contain significant amounts of protein.  For this reason, contact with cold pressed oils can cause allergic reactions if you are allergic to the nut or seed used to produce the oil.Untitled design (42) (1)Untitled design (43) (1)

Storm Trooper Food Allergy

Food Allergy for Beginners: Proteins

A Few Introductory Facts

  • Living things, including you and the food you eat, are made up of proteins, fats, sugars (carbohydrates) and minerals.
  • For the most part proteins – not sugars, fats, or minerals- cause food allergies.
  • Proteins are like Lego creations. They are large, complex structures made up of a slew of small, simple units (amino acids) stuck together.
    Amino Acid

    Single Amino Acid

    Protein Structure

    Protein Structure containing hundreds of amino acids.

     

  • A Millennium Falcon made out of red, green, yellow, blue, and white Lego pieces put together in a particular way “looks” like a Millennium Falcon.

Mellinium falcon lego

 

  • A pile of colorful, unconnected Lego pieces does not.

 

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  • Our immune system “sees” protein like we see a Lego-block Millennium Falcon, It does not recognize unconnected amino acids.
  • To stay healthy your body needs amino acids from the food you eat. It does not need intact proteins.
  • If your immune system decides that proteins looking like the Millennium Falcon are a threat, it may launch an attack with sophisticated weapons that go off when in contact with any Millennium falcon-looking food taking you down the dark path to… Allergy!

 

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Oral Desensitization for Peanut Allergy

This week the Lancet reported results of an oral desensitization study in children with peanut allergy.   Peanut allergic children age 7-16 were gradually exposed to increasing oral doses of peanut over a six month period.  The goal of the study was to achieve a level of desensitization that would allow the children to safely ingest 1400 mg of peanut protein (about 10 peanuts) without symptoms.

At the end of the study period, 62% of the children had reached the target goal and were able to tolerate 1400 mg of peanut protein. 84% were able to tolerate 800 mg of peanut protein, the equivalent of about five peanuts.  In the untreated control group, none of the children were able to tolerate the full dose of peanut protein.  Side effects in the group receiving peanut including vomiting, itching of the mouth and wheezing.  One child had an allergic reaction to the peanut severe enough to require an injection of epinephrine.

This is another study showing that oral desensitization to peanut in peanut allergic children can be successful and relatively safe.  The process does require significant time and effort and is associated with some risk.  It is a procedure that cannot be undertaken at home and requires careful monitoring in an allergy specialist’s clinic or hospital setting.

Is it worth the effort?  Currently, oral desensitization may significantly reduce the risk of a life threatening allergic reaction occurring in a peanut allergic child who is exposed to peanut by mistake.   The procedure is not a cure and does not allow children to enjoy peanut butter or a granola bar without concern of a reaction.

Progress in the Treatment of Food Allergy

Immunotherapy is a form of treatment in which small amounts an allergen (pollen, mold, or animal dander) is given to an allergic patient in slowly increasing doses to induce long-lasting tolerance to that allergen.  Immunotherapy is very effective in reducing allergy symptoms and is the closest treatment that we have to a cure. The trick is to be able to safely deliver a substance that a patient is very allergic to (usually a protein) in a manner that allows the immune system time to develop a protective tolerance response without triggering an allergic reaction.  This is routinely accomplished with allergy shots for airborne allergens.  Unfortunately, efforts to treat life-threatening food allergy with immunotherapy without triggering a severe and possible fatal allergic reaction have had limited success.

One of the goals of research efforts in food allergy has been to develop a food look-alike protein – one that can stimulate an effective tolerance response to a food but without the ability to trigger an allergic reaction.   Somewhat like a novice sword fighter  using wooden swords to train until he is experienced enough to handle the real thing.

Recently researchers at The Centre for Plant Biotechnology and Genomics in Spain have developed three hypoallergenic variants of the protein most commonly responsible for allergic reactions to peach (Pru p 3).  Peach is the most common food allergy in Spain and Mediterranean region.   The hope is that these proteins can be used safely as a vaccine in specific immunotherapy to treat patients with allergy to peach for whom the only currently available treatment is life long avoidance.

When You Should Give In To Your Craving for a Snickers Bar

For the past decade, pediatricians have recommended avoiding peanuts and tree nuts during pregnancy because of the concern that exposure to an allergen at this time might increase the likelihood of the baby having a food allergy, particularly if there is a strong family history of nut allergy.  In spite of these recommendations, not only did the prevalence of allergies fail to decline, but significantly increased during this period, with reported cases of nut allergy tripling from 1997 to 2010   Noting this disturbing trend, in 2008 the American Academy of Pediatricians withdrew their recommendation to avoid any foods during pregnancy to prevent food allergy.

And now, a recent study from Boston Children’s Hospital suggests that eating nuts during pregnancy can actually decrease the risk of allergy in their children.  This study found that the children of moms who ate five or more servings of peanuts and tree nuts a week were less likely to develop allergies to these foods than kids whose mothers ate less than one serving a month.   Pregnant mothers who are allergic to nuts, of course, should continue to avoid these foods.

The results of this study highlights a principle that has become clearer over the past several years as more research is directed at the growing problem of food allergy: withholding exposure to an allergen, particularly in young  children may end up causing the problem that we are trying to prevent.

Alien Allergy Attack from the Planet Alpha-Gal

It sounds like science fiction.  A hideous blood-sucking alien creeps into the bedroom of an unsuspecting victim while they sleep.  With razor sharp fangs the monster begins to feed, injecting a cocktail of chemicals to keep the blood flowing. As the fiend’s venom works it’s way through the body, a frightening change takes hold.  Forever transformed, the victim is doomed to live in fear of pleasures he once enjoyed.

As bizarre as it sounds, this scary story (with a few embellishments) is not science fiction but true.  Here are the unsettling details.

The blood sucking alien is Amblyomma americanum – the lone star tick.  The tick is found primarily in the Southeastern part of the United States, although some believe that it’s territory may extend further west.  In some individuals, a bite from the tick triggers the immune system to produce antibodies to a sugar found in the saliva of the tick called galactose-α-1,3-galactose or alpha-gal.   This sugar is also found in meats such as beef, lamb, and pork and so once a victim becomes “immunized” by the tick bite, eating a steak, for example, can cause hives or even more severe allergic symptoms.

Unlike most allergic reactions to foods, the alpha-gal reaction can occur 4-6 hours after eating meat.  And although a blood test for the alpha-gal antibody is available, it may not be ordered if the connection between a patients severe allergic reaction and eating a hamburger six hours earlier is not made. To make matters worse, patients who have become sensitized to alpha-gal by a tick bite can also have severe allergic reactions to cetuximab, a new medication used to treat cancer.

So far, the only treatment for alpha-gal sensitivity and the resulting meat allergy is avoidance.

Food Allergy Boot Camp

In sports and other competitive pursuits the saying “whatever does not kill you makes you stronger” seems appropriate and possible even comforting.  To have this applied to the topic of food allergy, particularly in children, seems anything but comforting.   Recent research aimed at understanding the complex problem of food allergy suggests that this principle may not be too far from the truth and underlies a significant paradigm shift in how we approach food allergy prevention.  The result is creating a squeeze felt by families with food allergies as well as the physicians who care for them.

Until recently, the American Academy of Pediatrics recommended that infants who were considered at increased risk of developing food allergy because of their family history should avoid peanuts during the first three years of life,  milk for the first year, egg until age two, and tree nuts and fish until three years of age. Also,  it was suggested that mothers avoid peanuts and other allergenic foods during pregnancy and breast-feeding.

Recently, however, these recommendations were withdrawn by the American Academy of Pediatrics because of a lack of current evidence supporting the assumption that delaying introduction of allergenic food helps to reduce the occurrence of food allergy and other allergic disease.  Also noted was a lack of evidence supporting dietary restrictions during pregnancy and breast feeding.  Even the World Health Organization’s strategy to prevent allergy by recommending exclusive beast-feeding for the first six months of an infants life has come into question.  Although breast feeding until four months of age is still recommended, evidence seems to suggest that prolonging breast feeding beyond 4 months of age may acutely increase the likelihood that a child will develop allergies!

So what options are available to parents and physicians to determine if a child is at risk of a serious food allergy because of a family history or other concerns and how can we prevent or reduce the likelihood of a serious food allergy from developing?

The “dual-allergen exposure hypothesis” is a new theory that may shed light on these questions .  This theory suggests that infants come into contact with small amounts of food through the skin as they explore the environment and as a result of this cutaneous contact, become sensitized.  Sensitization is the process of developing allergic antibodies to something in the environment.  These allergy causing antibodies can be detected on an allergy skin test or blood test.

Sensitization does not always lead to clinical allergy.  Why not?  Because between sensitization and allergy symptoms is a third factor:  tolerance.  Tolerance is our bodies way of reining in the inappropriate allergic response, preventing inflammation that we experience as symptoms.  We want tolerance: it’s natural and very effective, and without it, we would be at risk of reacting to many of the foods that we require for adequate nutrition.

The second part of the dual-allergen exposure hypothesis states that, although sensitization may occur through the skin, tolerance occurs through oral exposure.  In other words, eating the food helps to prevent allergies from developing.  The timing and balance of cutaneous and oral exposure determines whether a child at risk will develop adequate tolerance or else develop harmful adverse reactions because of allergy.

The dual-allergen exposure hypothesis has important implications for the use of allergy blood tests in children.  The use of blood tests to diagnose food allergy in children may in fact be causing more severe allergy problems because parents are frequently told to restrict from the diet foods that show up on a blood test (indicting sensitization but not necessarily allergy) and in the process, push the child from sensitization to true food allergy.

There is always some risk when a child is exposed to a food for the first time (as there is with taking their first step or attending their first day of school), but in spite of the risk of a few bumps along the way, early oral exposure to a food may in the end make the child stronger and less vulnerable to more serious food allergies in the future.

Define Your Terms

“If you wish to converse with me,” said Voltaire, “define your terms”.

In my practice as an allergy specialist, I find the principle of first defining terms before beginning a discussion with a patient to be key.  Particularly the term “allergy”.   “Allergy” is a very common word, frequently used in general conversation, therefore its definition should be fairly clear.  But this may not always be the case, and subtleties of variance in how we define this term can lead to significant misunderstanding.

From an immunologist’s point of view, a scientific definition of allergy could go something like this:

“Allergy is a  hypersensitivity disorder of the immune system which occurs when a person’s immune system reacts to normally harmless substances in the environment. These reactions are acquired, predictable, and rapid. Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity. Allergic reactions are distinctive because of excessive activation of certain white blood cells called mast cells and basophils by a type of antibody called Immunoglobulin E (IgE). This reaction results in an inflammatory response which an range from uncomfortable to dangerous”.

In this definition there are a few key points.  Allergy is reaction to specific substances involving a class of antibodies call IgE,resulting in symptoms.

A more conventional, laymen definition of allergy might look like this:  “An allergy is a reaction of the body to something that you eat, drink, breath or come into contact with that makes you itch, sneeze, wheeze, break out in a rash, get a stomach ache, or swell up”.

There are several medical problems that clearly meet this definition of allergy but in fact, are not allergy at all.  An example of this is lactose intolerance.   This is a problem with mammalian milk (cow, goat, even human) which is caused by the lack of an enzyme which is required to digest milk sugar.    Without this enzyme to turn the big lactose sugar molecule into its much smaller and absorbable bits, drinking milk will cause uncomfortable intestinal bloating, gas, and pain.  Although this a clear reaction to a food, no antibodies are involved,  so it is not an allergy.

Another example is Celiac disease.  In  this rare condition, patients become very ill with abdominal cramping, diarrhea, and even severe weight loss when exposed to even small amounts of gluten in their diet.  This difficult condition is definitely caused by an antibody reaction to a particular food, although the antibody is IgA, not IgE, and is therefore by definition, not an allergy.

Allergy has also been defined in terms of a result on a laboratory test  as well as in terms of symptoms.  For example, if a patient has a laboratory blood test that looks for IgE antibodies to food, any positive result might be viewed as proof of a food allergy.   However,  our definition of  allergy also  requires the presence of symptoms.     When a patient shows evidence of IgE antibodies to a food on an allergy test, we use the term “sensitization”.    A blood test for food allergy may show multiple sensitivities, but unless there is a history of adverse symptoms caused by a particular food, there is no allergy.    This means that you could be “sensitized” to something without being “allergic”, but you cannot be allergic if you are not sensitized.   Essential to the diagnosis of food allergy is the presence of symptoms caused by exposure to a food and laboratory evidence (skin test or blood test) of anti-food IgE antibodies.

Sensitivity, the antibody response on a laboratory test for allergy,  is an important definition to keep in mind when we discuss other tests for food allergy, such as the IgG test.  This test is commonly used in Naturopathic  Medicine, a form of alternative medicine, that places a strong emphasis on the role of diet  and food allergy in health and well being. IgG, like IgE, is a class of antibodies produced by our immune system.  Unlike IgE, IgG’s primary job is to defend against infections such as viruses and bacteria.  When you get a flu shot you are boosting the bodies production of anti-flu virus IgG antibodies.  When the real flu tries to invade and make you sick, the anti-flu IgG antibodies are ready to squash them.    Results of these IgG tests for food allergy frequently return a long list of positive reactions, and patients, upon seeing this list, frequently ask the question, “so what am I supposed to eat if I am allergic to all these foods”.

It does seem strange that our bodies would produce antibodies to a food if there is not a problem of some kind. Why would our immune system react to a food unless it had an issue with it, even if I am not aware of a problem or what that issue is?  Naturopaths use this line of reasoning to suggest that some foods cause “hidden allergy” and can be a source of inflammation.  This inflammation could lead to a variety of chronic conditions such as fatigue, headaches, weight gain, depression, mental fogginess, and many others.  However, this assumption is often a misunderstanding.  Some experts believe that the IgG antibody response occurs to the foods we eat the most and may play a role in the proper development of tolerance.  Tolerance is a good thing. Therefore the IgG food allergy test may simply reflect the foods that we eat most commonly, rather than being harmful.  For this reason, most experts agree that the IgG test for food  allergy is unhelpful and may in fact lead to excessive and dangerous food restriction diets.