Food Allergy & Sensitivity Testing: What You Need Know

Updated: Apr 29

Do you sometimes feel like you're reacting 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).

Perhaps you've seen an allergy specialist and you're aware of skin prick testing. They may have also performed 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 s