The Difference Between Food Allergy, Sensitivity, and Intolerance and Why it Matters

by Dr. Susan Tanner, MD

The typical expression of what most of us think of as an allergy is usually manifest as a rash, itching, hives, or, in more severe cases, as extreme swelling of respiratory passages and wheezing that can become life threatening.  Thankfully, these types of allergic reactions are not terribly common, and become increasingly recognizable as to the cause.  Avoidance, while sometimes inconvenient, is usually do-able and the best plan of action.

Where things get a bit cloudier is in the realm of delayed allergy, intolerance, and general sensitivity.  The difference lies in the specific way that the body’s immune system and autonomic nervous system responds to the irritant.  Allergies that manifest with an immediate response are generally governed by Immunoglobulin E, or IgE.  These allergens include many of the pollens, grasses, weeds, molds, and some foods.  They can also include chemicals or additives contained in foods, skin products, and toothpaste.

Allergies Explained

Other, delayed allergies cause a response in Immunoglobulin G, or IgG. Among these IgG antibodies are several subtypes, (just to make things more complex!), numbered, 1-4.   All of these can be behind both delayed reactions as well as a cross-sensitivity with certain IgE allergies.  That is to say that if one has an IgE allergy to say, birch pollen, then stimulation to the IgG4 system can result in certain food allergies that are in the delayed realm, such as milk, eggs, or apples.   An interesting study expanding upon this concept was published in March 2018, in Russia, by Voloshin, Smoldovskaya, et al. The study showed patterns of food allergies that appeared regionally in response to common IgE inhalant allergies among children.  The importance of this study suggests a big link between environment and subsequent development of food allergies that may be less dramatic in their presentation, but, nevertheless, very impactful on health in general.  Our takeaway from this is that if the environment has clean air, then the inhabitants’ tendency to form food allergies is also significantly decreased.

A wonderful book on the subject of allergies, entitled Allergy and Cross-Reactivity by Sue Killian and John McMichael.  If you have allergies, it is well worth reading.  I know both the authors personally and know the labor and research that went into producing the book.  Ms. Killian has traced down many allergies, likely IgG4, that cross react with other molecules.  Mesquite, interestingly, seems to be a universal reactor.  If allergy desensitization can be done with mesquite, it can dramatically reduce allergic symptoms to many other foods and inhalants.  Some chemicals have also been found to mimic food allergies; apples and formaldehyde for example, and this was also found in her research.

Gut Permeability (aka Leaky Gut) and Food Reactions

IgG4 allergies can also arise from increased pressure on the immune system of the gut.  Previously we have described the importance of maintaining a healthy gut lining for immune tolerance.  This lining can become damaged by toxins, such as mycotoxins from molds, chemicals, poor diet, and overgrowth of undesirable yeast and mold.  When the gut lining is damaged, large molecules of foods are absorbed into the bloodstream, recognized as a foreign invader, and the IgG response kicks in—this is often referred to as leaky gut. This is all for protection, but unfortunately manifests in many negative health symptoms.  Symptoms can be subtle such as fatigue, headache, brain fog, muscle aches and pains, or can be more dramatic such as irritable bowel function, rashes, and chronic respiratory symptoms.

Diagnosing Food Sensitivities

Determining IgG food allergies is best done by blood test. I prefer a lab that tests all subclasses of IgG, such as that done by Great Plains laboratory.  What I generally find, however, is that if a patient has a lot of gut disruption, they will show reaction to the foods that they eat most frequently.  Elimination of these foods while also removing the toxins and restoring the normal immune lining of the gut is the mainstay of treatment. For treatment, we usually recommend a 4-day rotation diet. With this plan, foods are rotated so that the body is not exposed to any one food but once every four days. Reducing the exposure keeps the immune system from overreacting as it heals.  Sounds complicated, but is totally manageable with forethought and planning. Patients that have the dedication and adherence to stick with it, find that the overall results can be dramatic.

Similarly, there are labs that test the white blood cell response in general and not the immunoglobulins.  ALCAT and Alletess are such labs.  Again, the larger the burden on the body, the more reactant the body is to foods.  Four-day rotational eating is also recommended for these results with elimination of the foods that are indicated with the highest reactivity. Most patients find that with cleaning up their environments (eliminating mold, toxins, chemicals, etc.) and simply rotating and/or avoiding those reactive foods, that their sensitivities subside, and they feel remarkably better rather quickly.

Food Intolerance

Finally, there is food intolerance.  This is when a patient knows he or she reacts to a substance, yet there is no test that shows it.  For odors and chemicals, these patients are often told that they have “vasomotor rhinitis, and are given a steroid nasal spray to treat the inflammation.  While this may help mitigate some symptoms, the cause is not being addressed.  This type of sensitivity is often found in patients in whom the system has become extremely burdened and the body load is great.  These are patients who absolutely must have the whole triad of “clean air, clean water, clean food” as their systems cannot tolerate even small amounts of stimulatory molecules.  In these patients, the autonomic nervous system has become sensitized through the olfactory nerve.  This reaction is not true allergy, but surely acts like it.  Chemically sensitive patients are often quite ill, frustrated, and tired of having their symptoms chalked up to psychosomatic illnesses.

For chemically sensitized and intolerant patients, besides avoidance, treatment of the gut lining, and cleaning up the environmental pressures, I have found several treatment methods that are effective.  Low dose antigen immunotherapy (LDA/LDI) is such a treatment but finding a practitioner can be difficult.  Sinus Defense, a homeopathic, transfer-factor treatment is also helpful.  Additionally, some patients have gotten great results with Nambudripad’s Allergy Elimination Techniques (NAET), an energetic method of treatment, but I have not been trained in or utilized this method.

Help for Allergies and Intolerances

Seeking care from an Environmental or Functional medicine doctor can help you figure out your allergies and reactivities.  The treatment plan may be long-term, but it does not take so much time to see valuable improvement! The right doctor can help you to pinpoint the disruptors in your diet and in your other exposures (air, water, etc.), and will find the treatment path that helps you recover. In the event that you cannot consult with a specialist in this area, putting yourself on a four-day rotation diet of the foods you eat most often may help in more ways than you realize, even with inhalant allergies as you are reducing that cross sensitivity. It is my opinion that you have nothing to lose by giving it a try. Additionally, never underestimate the importance of the quality of the air you breathe in healing your gut lining. Like the Russian study illustrates, the more toxins that are being frequently inhaled (mold, chemicals, microbes, smoke, pollen, dust, etc.), the more apt the body is to react to other things, like foods. Thus, testing and purifying your indoor air and making sure it is as free as possible from mold, particulates, chemicals, and other toxins has a HUGE positive impact on your health.

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