Allergy/Intolerance Testing: Different Methods and how they work

I recently had some blood work done to determine which foods my body is intolerant to. My mother asked me how they could identify food sensitivities by drawing blood, and what the difference was between this and the scratch test. I thought these were great questions that many people were likely wondering themselves when it comes to allergy testing.


IgG food reactions differ significantly from classic IgE food allergies. IgE food allergies are immediate reactions that occur within minutes or hours of consuming a food and may include serious reactions like hives, difficulty breathing and anaphylaxis. In contrast, an IgG food sensitivity is a delayed reaction that occurs hours to days after the food is consumed, with symptoms that may not appear for days or months.

Testing Options

A skin prick test, also called a puncture or scratch test, checks for immediate IgE allergic reactions to as many as 40 different substances at once. This test is usually done to identify allergies to pollen, mold, pet dander, dust mites and common allergenic foods.

Blood tests measure the levels of IgG in the blood. When a reactive food is consumed, the IgG antibody forms a complex with the food. Normally, the body is able to eliminate these antibody-food complexes, but with excess consumption of these foods, small complexes tend to deposit in blood vessel walls where they can cause tissue injury via the release of inflammatory mediators. Over time, this tissue injury may contribute to the development of a variety of health conditions. Research has shown that elimination of IgG reactive foods from the diet improves a variety of health conditions including irritable bowel syndrome, migraine headaches, eczema, mood disturbances, weight gain and other digestive disturbances.

Lack of an IgG antibody response to a specific food does not rule out the possibility that the food may elicit an IgE reaction, and vice versa. These are 2 separate physiological reactions that have their own set of cascading effects.

We also need to keep in mind that no test is perfect. We need to listen to our bodies.  No allergy tests, regardless of methodology, are as accurate as conducting your own elimination diet and documenting your progress in a food journal.

If you suspect an allergy or food sensitivity and not sure where to start, book an appointment with me and we can evaluate your situation, send you for testing (optional), and create a simple, realistic game plan that will set you up for success and lasting change.

I wish you clarity, self-empowerment and success on your journey to self-discovery and optimal health.



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