Understanding Food Allergies, Sensitivities, and Reactions*

Healthy individuals typically do not experience negative reactions to the foods they eat. Their bodies are able to digest a variety of foods efficiently, absorb nutrients as needed, and develop a process known as oral tolerance, in which the immune system recognizes these foods without reacting against them.

The exact percentage of individuals with food allergies or sensitivities is not fully known, as many people may not link their symptoms to the foods they consume. Nonetheless, research indicates that food reactions are relatively common and that the prevalence of food allergies appears to be increasing¹.

The European Academy of Allergy and Clinical Immunology (EAACI) defines an allergy as a “hypersensitivity reaction initiated by immunologic mechanisms”². This definition includes reactions mediated by antibodies (such as IgG, IgA, IgM, or IgE) as well as cell-mediated reactions, for example, skin outbreaks like contact dermatitis. While IgE-mediated reactions are considered classic food allergies, the EAACI notes that food-specific IgG antibodies generally indicate prior exposure rather than clinical allergy. Reactions involving IgE are classified as IgE-mediated food allergies, while other immune responses are typically categorized as non-allergic food hypersensitivities. Hypersensitivity is defined as “objectively reproducible symptoms or signs initiated by exposure to a defined stimulus at a dose tolerated by normal individuals”³.

Based on these definitions, reactions involving IgG or IgA antibodies are usually classified as food sensitivities. The clinical importance of IgG and IgA antibodies is still being studied and debated in the scientific community⁴.

IgE-associated reactions can include immediate-type gastrointestinal hypersensitivity, oral allergy syndrome, acute hives or angioedema, allergic rhinitis, bronchospasm, and in severe cases, anaphylaxis. Symptoms may involve skin reddening, itching, swelling of lips or eyelids, throat tightness, wheezing, difficulty breathing, coughing, vomiting, or diarrhea⁵⁶. These symptoms usually appear shortly after consuming the triggering food.

From a functional nutrition perspective, practitioners often consider a broader range of food-related reactions that can affect many body systems. Reported symptoms may include diarrhea, constipation, bloating, gas, urinary irritation, skin conditions such as eczema or psoriasis, tinnitus, nasal congestion, chronic sinus or ear infections, joint aches, headaches, brain fog, fatigue, and mood changes⁷⁸⁹¹⁰. These reactions can sometimes be delayed, appearing days or even weeks after consuming certain foods, particularly when mediated by IgA or IgG antibodies.

For individuals planning pregnancy, some health experts recommend reviewing and potentially adjusting dietary habits to reduce exposure to foods that may cause reactions. Optimizing nutrition and lifestyle during this period may support overall physiological function and provide favorable conditions for a healthy pregnancy and the development of the baby’s immune system.

References:

1. Sampson HA. Update on food allergy. J Allergy Clin Immunol. 2004.

   Burks AW, et al. Atopic dermatitis and food hypersensitivity reactions. J Pediatr. 1998.

2. Johansson SG, et al. Revised nomenclature for allergy for global use: Report of The Nomenclature Review Committee of the World Allergy Organization, October 2003.

3. Bernardi D, et al. Time to reconsider the clinical value of immunoglobulin G4 to foods? Clin Chem Lab Med. 2008.

4. Bock S, et al. Studies of hypersensitivity reactions to foods in infants and children. J Allergy Clin Immunol. 1978.

5. Sampson HA, Burks AW. Mechanisms of food allergy. Annu Rev Nutr. 1996.

6. Bentley SJ, Pearson DJ, Rix KJ. Food hypersensitivity in irritable bowel syndrome. Lancet. 1983.

7. Firer MA, Hosking CS, Hill DJ. Cow’s milk allergy and eczema: patterns of the antibody response to cow’s milk in allergic skin disease. Clin Allergy. 1982.

8. Jones VA, et al. Food intolerance: a major factor in the pathogenesis of irritable bowel syndrome. Lancet. 1982.

9. Vojdani A. Detection of IgE, IgG, IgA, and IgM antibodies against raw and processed food antigens. Nutr Metab (Lond). 2009.

*Disclaimer: None of the information written on this blog is intended to diagnose, treat, cure, or prevent any disease. This information here on in are for health maintenance and for educational purposes only. Nothing in this information provided is intended to replace conventional medical approaches. Please consult with your current medical health care provider before deciding to change your diet and lifestyle.