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Food Allergy & Sensitivity Testing: What You Need Know

Updated: May 30, 2022

Do you sometimes feel like you react to everything? You just can't seem to pinpoint what food your body can or cannot tolerate. Perhaps you've got eczema or acne. Maybe you're struggling with irritable bowel syndrome symptoms. Or joint pain, sinusitis, depression, fatigue, and brain fog which can also be symptoms of a food sensitivity.

So, how can we clear up the confusion and what tests are available for food allergies, sensitivities and intolerances? (If you're not clear how to differentiate between these three terms I recommend reading this first).

If you've seen an allergy specialist, you may be aware of skin prick testing or you may have had IgE allergy blood tests. A GP or dietitian might have recommended an elimination diet. A naturopath or functional medicine practitioner might have suggested ALCAT, ELISA or more comprehensive Immunologic Allergy Testing. Then there is applied kinesiology (AK) muscle testing or hair analysis.

So, what's the difference? What are the advantages and disadvantages of each test? Let's take a look...

Skin prick testing

How is it tested?

A shallow scratch is made on the skin of the forearm or back and then a small amount of an extract of a potential allergen is placed in it. If a hive or a wheal occurs on the scratch, it's considered a positive result. The size of the hive may correlate with intensity of allergic reaction.

Anti-histamines and steroids are best avoided for a few days prior to the test.

What is it testing?

Assesses IgE mediated allergic reactions only.

In true allergies, IgE (immunoglobulin E) antibodies are released by the immune system.

The IgE antibodies trigger mast cells, which line the surface of the body under the skin and internally around major organs, to release inflammatory chemicals including histamine. These chemicals cause the symptoms of allergic reactions, such as itchy skin and swelling.

What are the benefits?

  • Severe reactions to a prick tests are uncommon.

  • A rescue medication can be on hand.

  • Used frequently by allergy specialists.

  • Can also be used for environmental allergens such as cat fur, pollen, and dust.

What are the disadvantages?

  • Only detecting true IgE allergies. Does not assess delayed hypersensitivity reactions which are more common.

  • False positives can occur due to cross-reactivity.

  • Only a small selection of foods are usually tested.

  • Requires seeing an allergy or immunology specialist.

IgE blood tests / RAST test

How is it tested?

Requires a blood draw.

What is it testing?

The radioallergosorbent (RAST) blood test is used to test IgE mediated allergies.

IgE (immunoglobulin E) are antibodies made by the immune system. Higher amounts can be found when the body over-reacts to allergens. Levels are often elevated in cases of allergic disease.

IgE antibodies are different depending on what they react to. An allergen-specific IgE test can show what the body is reacting to. This is the blood test version of the skin prick test.

What are the benefits?

  • Assesses IgE-mediated allergies.

  • No risk of an adverse reaction as assessed from blood drawn.

What are the disadvantages?

  • Only looks at immediate IgE reactions.

  • If tested through an allergy specialist, only a small selection of foods are often assessed.

Intradermal test

How is it tested?

A very small amount of a suspected allergen is injected under the skin. Signs of reactivity are observed. This test is similar to skin prick testing.

What is it testing?

Ig E mediated allergic reactions.

What are the benefits?

  • Assessing IgE allergy reactions and is used by allergy specialists.

  • Is considered more sensitive than skin prick test.

What are the disadvantages?

  • Chance of a severe adverse reaction. This procedure can only be performed by an allergy specialist and is supervised more closely than skin prick testing.

  • False positives can still occur.

  • Testing IgE allergies not IgG or IgA delayed reactions.

  • Not usually used for assessing food allergies but to diagnose drugs and insect allergy.

Elimination Diet

How is it tested?

Foods which are suspected allergens or sensitivities are avoided in the diet. If symptoms subside while avoiding and then return on reintroduction (preferably with a double blind food challenge) that can indicate a food allergy, sensitivity or intolerance.

What is it testing?

Allergies (IgE mediated), sensitivities (non-IgE mediated immune reactions) and intolerances (due to a breakdown in gut function).

What are the benefits?

  • If done for long enough can also indicate not just IgE food allergies but also delayed hypersensitivity reactions and food intolerances. (But don't know which one).

  • Anyone can follow an elimination diet. It does not require seeing an allergy specialist.

  • Non-invasive.

What are the disadvantages?

  • Best used to confirm other tests.

  • Time consuming and laborious.

  • Difficult to assess if multiple food allergens are present. If no improvement in symptoms, could there be another allergen involved?

  • The food needs to be strictly avoided, not just reduced in consumption.

  • If symptoms improve, this does not mean you have addressed the problem. Improved gut health may still be required.

Immunologic Allergy Testing / ELISA

How is it tested?

Through blood draw or blood spot. Blood spots tests can be done at home where just a small sample of blood is required from a finger prick. A blood draw involves seeing a phlebotomist for a small fee at a lab testing clinic.

What is it testing?

This specialized blood test (using ELISA - enzyme linked immunosorbent assay) can assess IgE, IgG, IgG4 (a specific subtype of IgG antibodies) and/or IgA antibody immune response to a selection of foods.

Some labs also assess complement (C3d) & blocking potential for a more comprehensive assessment, which is thought to remove the likelihood of false positives.

Reaction to the specified food is thought to worsen if C3d complement activation is present along with an IgG antibody response. Complement may increase the inflammatory potential of a reaction to the food by 1000 to 10,000 fold!" (1)

Blocking potential can occur if IgG4 levels are greater than IgE for a particular food. The IgG4 then blocks the IgE receptor sites and reduces the severity of symptoms of an IgE allergy reaction.

What are the benefits?

  • Depending on the test it can assess IgE allergy reactions or delayed hypersensitivity reactions (IgG or IgA). Delayed hypersensitivity food reactions are the most common, and IgG testing is thought to be the main way of assessing them.

  • Can detect unsuspected or hidden food sensitivities and can be beneficial for prevention of further illness.

  • Several clinical studies have shown that elimination of IgG-positive foods can improve symptoms, including those with irritable bowel syndrome, autism, cystic fibrosis, and rheumatoid arthritis. (2, 3, 4, 5, 6, 7, 8)

  • No risk of an adverse reaction as assessed from blood drawn or blood spot.

  • Assesses around 100 different foods.

  • Some of the labs only assess one subtype of IgG called IgG4. The reliability of the IgG4 test is thought to vary between 80 to 90%. (9)

  • Tests that include IgE, total IgG, IgG4, blocking potential and complement (C3b) can offer a very comprehensive assessment of food allergies and sensitivities. (Such as the one by Precision Point Diagnostics called P88 Dietary Antigen test).

What are the disadvantages?

  • NOT available through your General Practitioner or Allergy Specialist as considered "unproven".

  • Can be expensive and often not covered by insurance.

  • Highest levels of IgG4 occur 1-3 days after exposure. Tiny amounts may not set off symptoms. So, if the food hasn’t been consumed for a long period of time, will it miss a sensitivity reaction? (eg. strawberries only eaten over summer).

  • Needs to be from a reputable licensed lab.

  • Each lab assesses differently.

  • Some scientists believe the production of IgG antibodies to foods is a normal immunologic phenomenon & therefore the test is irrelevant. Others say it’s not normal for someone to have high levels of IgG antibodies against foods.

The benefits of IgG food testing were illustrated in an early article published by an otolaryngologist. He reported that the majority of his patients had substantial health improvements after eliminating foods found positive by IgG food allergy testing. The overall results demonstrated a 71% success rate for all symptoms achieving at least a 75% improvement level. (10)

ALCAT – Antigen Leukocyte cellular Antibody Test

How is it tested?

Requires a blood draw.

What is it testing?

Measures leukocyte cellular reactivity (degranulation within the white blood cells) in whole blood, which is the final common pathway in all allergy/sensitivity mechanisms.

Degranulation is a precursor to an immune response.

Used to assess reactions to foods, food additives, chemicals, drugs and even moulds.

What are the benefits?

  • Apparently it “Is the only test shown to correlate with clinical symptoms by double blind oral challenges, the gold standard”. (11)

  • Thought to measure delayed reactions to foods.

  • Measures immune, non-immune and toxic reactions to the foods.

  • Can assess up to 200 different foods, and even chemicals & moulds.

  • May be covered (at least in part) by insurance.

What are the disadvantages?

  • Can be expensive.

  • Not assessing immediate Ig E reactions.

  • Not specifically measuring IgG & IgA reactions.

  • No consideration of complement or blocking potential.

  • Unproven. Although the apparatus (Coulter counter) is validated, data are not available on technical parameters which puts the sensitivity and accuracy of the test into question.

Applied kinesiology (AK) or kinesiology testing

How is it tested and what is it testing?

Uses muscle testing to determine if a food is detrimental to that person. A normotonic muscle will weaken on exposure to that food. Isodes can also be used in the assessment. These are highly diluted homeopathic preparations of a disease, nutrient, chemical or food.

What are the benefits?

  • Avoids the need for a blood draw.

  • Is relatively inexpensive.

  • Can take into account food allergies, sensitivities and intolerances. All other tests only consider allergies or sensitivities.

  • Other assessments can be done at the same time such as looking at gut health, parasites, bacteria, viruses and increased intestinal permeability.

  • Can test groups of food antigens (e.g. nightshades, salicylates) or individual foods.

What are the disadvantages?

  • Unproven and currently not supported by scientific studies.

  • Is the skill of the practitioner a factor?

  • Viewed as more accurate when the food is placed on the tongue, which is not safe if a true IgE allergy is suspected.

  • If not consuming the food, a false negative may occur.

Hair analysis

How is it tested and what is it testing?

Uses a small sample of hair to assess food allergies, sensitivities and intolerances. Some labs offer chemical, heavy metal and nutritional testing also. The hair sample should be from close to the scalp and equivalent to half a teaspoon of hair.

What are the benefits?

  • Affordable

  • Claims to assess food allergies, sensitivities and intolerances.

  • Non-invasive and easy to send in.

What are the disadvantages?

  • Unproven. Retests have shown different results.

  • Unstandardised

Final comment...

Unfortunately no test has all the answers. There is a chance of false positives or false negatives with any test.

The medical profession will typically only consider use of skin prick, intradermal and IgE testing. However these only assess IgE mediated allergies and leaves the vast majority of reactions to foods (which are delayed) to be assessed by the laborious and time consuming elimination diet. No wonder people are seeking other alternatives!

Although not scientifically validated I have had success using immunologic testing and applied kinesiology muscle testing to help uncover allergies, hidden food sensitivities and intolerances in my clients. However, I do understand the hesitation in relying on such tests.

Hopefully in the future, there will be more studies to back them.

Discover some of the functional medicine lab tests I recommend by clicking below:

Keen to work with me to address your gut health, eczema or food sensitivities?


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