Special Interests

IgG Food Intolerances

There is growing evidence that food-specific IgG antibodies can be associated with many chronic health conditions. Our body’s defense system can be expected to produce some levels of IgG antibodies to specific foods, and to combine proteins with the foods to form complex molecules, cross the intestinal wall, and enter the bloodstream. When the immune system is working well, these complexes are destroyed by macrophages. However, if there is an overload or a flawed immune system, these complex molecules can circulate in the bloodstream, deposit, and accumulate in various tissues, leading to inflammation and a myriad of chronic diseases.

The diseases and conditions that have been associated with raised levels of food IgG antibodies:

  • Irritable bowel syndrome
  • Inflammatory conditions such as arthritis
  • Migraines and headaches
  • Respiratory diseases such as asthma
  • Gastrointestinal: Bloating, gas, constipation, diarrhea
  • Tiredness, not feeling well
  • Rashes, eczema
  • Obesity

It can be challenging to identify the food(s) that are linked to the symptoms. IgG food sensitivities are typically a delayed reaction which means the symptoms may not appear for days, making it hard to identify them. Elimination diets are based on guesswork and can take a lot longer to determine which foods are causing the issue.


It is essential to understand the role that cross-reactivity plays in the interpretation of results. Cross-reactivity occurs when the immune system reacts to a similar or identical protein of other foods or pollens. These are known as pan allergens. If there is a 70% similarity, cross-reactivity can lead to an increased result, even if the patient has not consumed the specific food. These reactions should not be considered a false positive because those results may reflect a pattern of clinical sensitivities, including the possibility of a pollen sensitivity.

Current publications focus on IgE antibodies; however, cross-reactivities can overlap between IgE and IgG antibodies, given their relationship. For example, it has been shown that birch pollen can have cross-reactivity with peanut, hazelnut, potato, soy, almonds, and foods that contain similar storage proteins, such as lentils, peas, and walnuts.