The Difference Between Food Sensitivity Tests and Food Allergy Tests

One of the more frustrating things that I experience as a Dietitian who works with people with food allergy is when people come to me with a lab report listing foods they are ‘allergic’ to — only for me to get a multi-page report that they paid $650-750 out of pocket for, and which measures IgG antibodies, not the IgE antibodies which are associated with food allergy. These people paid good money to find out what foods underlie them not feeling well and received an impressive looking multi-page document that doesn’t measure what they think — or are led to believe it measures.

Our body makes different types of antibodies, including IgA antibodies, IgG antibodies, IgM antibodies, and IgE antibodies. IgA antibodies are found in high concentrations in the respiratory passages, as well as the GI tract and one of the best known IgA antibody tests is the IgA TTG test which tests for whether someone has celiac disease. IgM antibodies are found in the blood and lymphatic system and are found when our body is fighting a new infection. IgE and IgG antibodies are covered below.

Immunoglobin E (IgE)

IgE antibodies are produced by the immune system and are normally found in very small amounts in the blood. When someone has an allergy — whether to an environmental substance such as pollen from trees or grasses, or to food, the body overreacts and produces high amounts of specific allergen IgE antibodies.  What is important to know is that each type of IgE is specific to one type of allergen. When the IgE antibody binds with our mast cells, a type of white blood cell that is part of our immune system, they release histamine which causes us to have an allergic reaction, which may be sneezing, itching, difficulty breathing, or other symptoms [1].

When people have some types of environmental allergies such as to pollen from grass or trees, they might be prescribed antihistamines to calm that allergic reaction down. 

When people are diagnosed with food allergies, they are advised to avoid that food completely, which is often sufficient to avoid symptoms. Sometimes completely different foods that have proteins with similar amino acid sequences as the food they are allergic to cause them to have a “cross-reaction”. This is where the body recognizes the similar amino acid sequence as being the same as part of the amino acid sequence in food that they are allergic to (and to which they have IgE antibodies).  In some cases the body will react to this other food as if it is allergic, but it is usually it a lower level of a reaction that the food to which they have a full-blown reaction.  

When people have very serious food allergies, they are advised to carry an Epipen in the event they have a very serious reaction called anaphylaxis.  Anaphylaxis is a serious, life-threatening allergic reaction where a person’s immune system over-reacts to a specific allergen (such as insect sting, peanut or latex) and which results in difficulty breathing and a sudden drop in blood pressure. This requires immediate medical treatment, including a person (or someone else) administers an Epipen injection which contains epinephrine (adrenaline) to get them breathing, and then a visit to the emergency department of a local hospital.

Tests for food allergy always involve assessing the amount of IgE antibody response to a specific allergen or allergens — either by skin-scratch testing, or by a specific antigen IgE blood test.

Immunoglobin G (IgG)

IgG antibodies are found in our blood and other body fluids and recognize foreign proteins — including those from bacterial and viral infections.  These are the type of antibodies we are looking for when we’ve had an vaccine or immunization to diseases like chicken pox, or measles.

Our body also produces IgG antibodies in response to foods — and this is a normal response in a person with a healthy immune system.

Our body knows the difference between the proteins it makes, and the proteins contained in our food, so if we eat beef or a banana, our body will make IgG antibodies to the proteins in those foods. These IgG antibodies serve as a form of “memory” of our exposure to that food. Positive IgG antibodies to a food do NOT indicate a food allergy [2]. A positive IgG antibody response to a food means that our body as been exposed to that food recently and recognizes the protein in it.

Food Sensitivity / Food Allergy Testing

Sometimes, people have symptoms that make them feel unwell and they want to determine which foods, or food-components underlie their symptoms.

If the person goes to their doctor, they may be referred to an Allergist who will determine if they have IgE mediated antibodies to specific proteins in various food.  If they do, the person may be advised to avoid eating these foods, or if a potentially serious food allergy, to carry an Epipen. They may be advised to see a Dietitian that specializes in food allergies to help them know which foods are similar to the ones they are allergic to (i.e. cross reactants), so they can minimize their symptoms.

Sometimes the person will go to a Dietitian that is experienced with food allergy first — in an attempt to determine if they are allergic or sensitive to specific foods.  After taking a thorough history — including whether the person is allergic to certain trees which are known to cross-react with specific vegetables, fruit or nuts, the Dietitian may be recommended the person ask their doctor to requisition specific antigen IgE blood tests to determine of they are allergic to a food or tree pollen that is known to underlie Oral Allergy Syndrome. Oral Allergy Syndrome is where the body recognizes amino acid sequences in certain foods that are similar to the tree pollen(s) they have IgE antibodies to.

Note: Specific antigen IgE antibody testing is completely covered by provincial health insurance. In British Columbia, general practitioner MDs / family physicians can requisition up to 5 specific antigen IgE blood tests per year per patient.

If the specific antigen IgE blood test results come back positive, then the doctor may refer the person to an Allergist for further testing, and the Dietitian will teach them about avoiding foods they are allergic to, as well as their cross-reactants.

Alternative Food Sensitivity Testing – immunoglobin G (IgG)

Sometimes, instead of going to their doctor or to a Dietitian experienced with food allergies, people will sometimes seek out the help of a Naturopath. Typically, they will recommend “food sensitivity testing”, for which they charge between $650-$750. In this type of testing, the person will have their blood drawn and sent off to one of several labs that do this type of testing. The blood is exposed to different types of foods, and food components in a petri dish and the degree to which immunoglobin G (IgG) binds to each food is measured. The results are then printed off in a multi-page report that is given to the person by their Naturopath who explains that the positive results indicate the degree to which the person has an “allergy” or “sensitivity” to those foods [2]. The problem is, IgG antibodies only indicate that the person’s body recognizes that foodNOT that they are allergic or sensitized to the food.

Note: Only IgE antibodies assess true allergy — either by skin scratch testing, or specific allergen IgE blood tests.

These multi-page reports come in different formats, and here are a couple of examples (with names removed);

Based on these results, people will be advised by their Naturopaths which food(s) they should avoid.

Sometimes the person is provided with accompanying information which lists specific conditions that are supposedly associated with positive IgG antibodies, including weight gain, bloating, hyperactivity, depression, asthma, high blood pressure and others [1].

Alternative Food Sensitivity Testing – MSAS Food Sensitivity Testing, Kinesiology Muscle Testing

There are other types of alternate testing that are supposed to indicate whether a person is “sensitive” to a food. The procedure called MSAS Food Sensitivity testing uses a device which conducts an electrical current on acupuncture points (called meridian points) on the fingers and arm.

Here is an example of MSAS report:

MSAS Food Sensitivity Testing Results

One client of mine was told by their Naturopath that they were allergic to food if their arm went down when they were rubbed gently with the food, while holding their arms out by their sides. This technique is known as Kinesiology Muscle Testing (unaffiliated with the health science of Kinesiology).

Food intolerance

Food Intolerance is non-IgE mediated food sensitivity which usually involves a difficulty in digesting certain foods, and often involves a lack of a specific enzyme.

Lactose Intolerance is a well-known food intolerance in which a person can’t digest the sugar in milk because they have a shortage of the enzyme, lactase. Primary lactose intolerance is where a person doesn’t make enough lactase, and secondary lactose intolerance is where the person lacks lactase because they’ve had diarrhea which sloughed off the lactase enzyme which resides in the intestinal wall.

Tyramine Intolerance is also caused by a lack of an enzyme — in this case monoamine oxidase (MAO). As a result, levels of tyramine can build up, causing migraine, heart palpitations or GI issues, including nausea and vomiting.

As mentioned above in the section about IgE mediated allergy, histamine is released from mast cells and mediates allergic reactions. Histamine is produced by the body, along with an enzyme known as diamine oxidase (DAO). DAO is responsible for breaking down histamine that is made from foods you eat that contain histadine. Some people have a deficiency of DAO, which is called histamine intolerance. It may be secondary to a person having Mast Cell Activation Disorder (MCAD), or due to some other cause, such as certain medications that cause them not to be able to break down histamine properly. In such cases, limiting foods that are high in histadine — which gets converted to histamine can be helpful, or by limiting foods that trigger histamine release from mast cells.

If You Think You May Be Allergic 

If you think you may be allergic to certain foods, or that some of the food you are eating may underlie specific symptoms you are experiencing, then go see your doctor and seek the help of  a Dietitian that specializes in food allergy and sensitivity.

The first step would be to rule out genuine food allergy, which is IgE antibody mediated. This can be done by scratch tests from an Allergist or by specific allergen IgE tests (both types of tests are covered by provincial health insurance). If you have food allergies, then the Dietitian will teach you how to avoid those foods, and how to watch out for cross-reacting foods.

If you don’t have food allergies, then the Dietitian can assist you in identifying which foods are making you feel unwell, then by recommending an appropriate approach once the specific foods, or food components are identified. For some, this may mean avoiding the food, but often times it is a matter of eating less of the food at a time, or eating it less often. Each person is different.

More Info?

If you think you may have food allergies or sensitivities, I offer a package called the Food Sensitivity Food Allergy Package which walks people through the process mentioned above.

If you have questions please send me a note through the Contact Me form on the tab above.

To your good health!

Joy

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References

  1. American Academy of Allergy, Asthma and Immunology, Immunoglobin E (IgE)  definition, https://www.aaaai.org/conditions-and-treatments/conditions-dictionary/immunoglobulin-e-(ige)
  2. American College of Allergy, Asthma and Immunology (ACAAI), Can IgG blood testing check for delayed food allergies?https://acaai.org/resources/connect/ask-allergist/can-igg-blood-testing-check-delayed-food-allergies
  3. Lavine E. Blood testing for sensitivity, allergy or intolerance to food. CMAJ. 2012;184(6):666-668. doi:10.1503/cmaj.110026

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