Food sensitivity testing is an essential tool in the Functional Medicine Approach to treating food sensitivities in children. Food sensitivities and intolerances are often mistaken for food allergies, but the reactions that occur in the body are not the same. Food allergies are immediate and can be life-threatening, while the onset of food sensitivities can be delayed by up to 48 hours, making the offending food especially difficult to pinpoint. 

Elimination diets can be used to reduce symptoms successfully but are challenging for anyone, especially kids. Using food sensitivity testing results while planning an elimination diet can allow for a wider variety of foods and, ideally, better results in a shorter period of time. 

Although this article will focus on food sensitivity testing and dietary protocols, it is important to consider the differences between food allergies, food intolerances, and food sensitivities to choose the best lab test and protocol for an individual.

Food Allergy (IgE Antibody-mediated immune reaction)

When a child has a food allergy, the body has a severe reaction to the protein component in that food. About 90% of food reactions occur in eight food groups: milk, soy, eggs, wheat, peanuts, tree nuts, fish, and shellfish. An allergic reaction is often immediate and can be severe or life-threatening. Immediate responses to food antigens are mediated by IgE antibodies. They are dependent on the activation of mast cells and other pro-inflammatory mediators in specific tissues, including the skin, respiratory tract, gastrointestinal, mucosal, and cardiovascular systems. Allergists will almost always make the diagnosis of food allergies in children.

Food Sensitivity (IgA, IgG, IgM antibody-mediated immune reaction)

With food sensitivities, the immune system reacts to specific proteins in food, but this delayed immune reaction to food antigens is mediated by IgG, IgA, and IgM antibodies. Unlike the immediate effects of IgE-mediated allergy, these reactions can take several days to appear, making it very difficult to identify which food the child is reacting to.

Food Intolerances (Non-Immune related factors)

The commonly used term food intolerance includes all bodily reactions that arise from NON-immune related factors. These reactions include:

• Enzyme deficiencies (ex. lactose intolerance)
• Chemical mediators in food that produce inflammatory reactions (such as the amines Histamine and Tyramine)
• Neuro-excitation by Glutamates 
• Detoxification impairments by Salicylates
• Physical gastrointestinal distress can be caused by the irritation and microbiome disruption (for example, a reaction to FODMAP foods)
• Reaction to food additives (such as MSG, preservatives, thickeners, emulsifiers, and stabilizers)

Note: *The terms food sensitivity and food intolerance are sometimes used interchangeably for all hypersensitivities that are not food allergies, as there is no standard definition. For the purposes of this article, food intolerances will include any adverse reaction to food that does not involve the immune system.

Food Sensitivity Signs & Symptoms 

After a food allergy is ruled out as the reason for a child's symptoms, food sensitivities may be explored as a cause. Chronic exposure to offending foods can stimulate immune cells and lead to antibody production, including IgG, IgA, and IgM antibodies. In particular, IgG antibodies bind directly to the food as it enters the bloodstream, forming food particles with the antibodies, which then circulate in the bloodstream producing inflammatory reactions that are non-specific in nature. 

This is different from a food allergy response in which IgE antibodies attach to mast cells and cause sudden-onset symptoms. The symptoms of a food sensitivity immune reaction are delayed and can appear anywhere from a couple of hours to several days after consuming the food. Because the response is delayed and widespread, a child with a food sensitivity may have multiple symptoms, not just one or two, localized to a specific organ, as observed in a food allergy. 

The symptoms can range from allergy-like reactions such as rashes and hives to gastrointestinal symptoms like stomach ache, constipation, and diarrhea, or neurological symptoms including headaches and migraines. 

This can make food sensitivities challenging to determine, and many individuals remain undiagnosed without an explanation or treatment for symptoms.

Symptoms of food sensitivities will vary for each child, the type of food that causes a reaction, and the amount of food eaten. One or all foods in a specific food group (ex., dairy) may cause food sensitivity.  

 Symptoms Include:

• Gas
• Bloating
• Fever
• Fatigue
• Abdominal pain
• Diarrhea
• Constipation
• Headaches
• Brain fog
• Rashes, such as eczema
• Nausea and vomiting
• Skin itchiness and redness
• Bronchitis and asthma-like symptoms
• Musculoskeletal joint pain
• Muscle stiffness and swelling

Possible Causes of Food Sensitivities in Kids

Leaky Gut 

Food sensitivities are thought to be related to increased intestinal permeability, also known as leaky gut. We all have some degree of permeability in our gut, as it serves to allow important nutrients into the bloodstream. In fact, some dietary proteins exit the gut fully intact, but non-response to these antigens is achieved through oral tolerance, and the body sees the food antigen as harmless and does not respond. However, if the barrier is compromised and the tight junctions in the gut become leaky, food molecules that are too large can escape and are detected by the immune system. 

Based on seminal research by Dr. Alessio Fasano, we now know that a protein called zonulin signals the tight junctions of the intestinal wall to open up, creating intestinal permeability. When the zonulin pathway is dysregulated, there is an associated risk of leaky gut, which is implicated in several diseases, including inflammatory bowel disease, celiac disease, type 1 diabetes, and other autoimmune conditions. 

A leaky gut can serve as a marker of the overall immune system function and increase the risk of future autoimmune diseases. The good news is that leaky gut is reversible, zonulin can be regulated, and improved gut barrier function and immunity can be achieved. A study showed improvement of symptoms with a diet that excluded the triggering food antigen, with improvements of 50% of people at four months and increasing to 74% after six months of the diet.

Impaired Digestion 

In combination with a leaky gut, improper digestion of food due to a lack of enzymes and stomach acid (which allows the body to break down and absorb nutrients from food properly) can contribute to a lack of oral tolerance. The immune system regulates the response to the antigens introduced, and foods that are not digested completely due to poor gut function form an unfamiliar food antigen that the body sees as foreign. This can result in the body being on high alert and reacting to many foods and toxins, not just one. A food sensitivity panel would reflect this with a high reaction to many foods.

Gut Dysbiosis 

There are multiple ways a child's microbiome can be influenced, contributing to immune function and gut health. Important factors include increased pesticide exposure- glyphosate specifically has been studied, GMOs (genetically modified organisms), hybridization of crops, and toxins in our environment. As a result of lifestyle and environmental changes, our immune systems may not have the opportunity to get exposed to various organisms that help it become strong. 

Dysbiosis arises when there's a general imbalance in the microbiome or a pathogen is present (ex. SIBO, H. pylori, candida, or parasite). Improved hygiene, antibiotic use, gut infections, and lack of fermented foods have been implicated in shifts in gut health in developed countries. This decline in the diversity of gut bacteria leads to an imbalance between the beneficial and harmful organisms in the body. Additionally, an increase of certain gram-negative bacteria in the gut can promote inflammation by releasing lipopolysaccharide (LPS), also known as endotoxins. Elevated LPS is a risk factor associated with increased inflammatory markers and chronic inflammation, contributing to a leaky gut. 

Inflammatory Foods

The primary cause of leaky gut is what we eat, especially inflammatory foods. While each person needs to find their own triggers, a diet high in the following foods can set the stage for inflammation, leading to leaky gut, dysbiosis, immune reactions, and subsequent food sensitivities. 

• Refined and processed oils and vegetable oils
• Margarine, shortening, and lard
• Refined carbohydrates, such as white bread and pastries
• French fries and other fried foods
• Processed meat (hot dogs, sausage)
• Sugars, including soda and other sugar-sweetened beverages
• Artificial sweeteners
• Emulsifiers, thickeners, and other food additives: Guar gum, carrageenan, xanthan gum, cellulose gum, and soy lecithin
• Foods containing additives, colorings, dyes, and preservatives (avoid non-specific ingredients such as "natural flavorings")

Children eat several times a day, which can result in continuous irritation to the gut. The related symptoms will remain until inflammatory foods and sources of specific food sensitivities are eliminated. 

The most common food allergies, also known as the "Big 8", are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans. 

This list can help guide possible food sensitivities as well. In addition, lectins and nightshades can contribute to inflammation in some people.

Gluten/Wheat 

Recent research shows an IgG antibody response to gluten occurs in non-celiac gluten sensitivity (NCGS). This is different from celiac disease, which usually tests for antibodies to only a few components found in gluten. People with NCGS can react with specific antibodies to many other components of wheat and gluten, including transglutaminase, gliadins, glutenins, gluteomorphins, wheat germ agglutinin protein, and peptides. This can lead to an autoimmune response to the gut, skin, brain, joints, liver, thyroid, bone, reproductive organs, and other areas of the body. 

Gluten can cause the gut cells to release zonulin, the protein that can break apart the tight junctions in the intestinal lining. For this reason, many functional health practitioners remove gluten from the diet for all individuals that experience food-related symptoms. 

If a child is shown to be reactive to gluten but is not finding improvement in symptoms with a gluten-free diet, consider contamination of non-gluten grains as a possible source of gluten and rule out cross-reactivity of other foods.

Cross-Reactive Foods 

Cross-reactivity is the concept that different antigens appear similar to the immune system. Some foods are recognized by the individual's body as gluten by mistake and produce an immune response in a person who is sensitive to gluten. Foods that the body can confuse with gluten because of a similar protein structure include:

• Dairy: Whole milk and isolated dairy proteins (casein, casomorphin, butyrophilin, and whey) can cross-react with gluten. 
• Corn: For some people, the protein in corn (maize prolamin) elicits a similar response to wheat gluten peptides. This can be important as corn is the most common alternative when removing gluten from the diet. 
• Many other grains have a similar molecular structure to gluten, including all cereal grains, millet, quinoa, amaranth, and rice. Practitioners often use an entirely grain-free diet to address possible food reactions, but testing for these cross-reactions is now an option. 
• Other foods that can cause cross-reactivity include soy, chocolate, coffee, sesame, and potato.

In addition to gluten cross-reactivity, there is also research on possible cross-reactivity among foods with a similar molecular structure. This can be helpful in considering the exclusion of foods that may not be tested on a specific food sensitivity panel (for example, cow's milk can cross-react with goat's milk). Cross-reactivity can also occur between food and human tissue, a concept known as molecular mimicry, which may contribute to various autoimmune diseases. The concept has been well studied in autoimmune thyroid disorders due to the prevalence of thyroid disease. Other autoimmune diseases are also being studied, and the body of research on this concept continues to grow over time. 

Food Sensitivity Tests For Kids

Considerations for choosing the best food sensitivity test for a child will depend on several factors, including:

• Preference for blood spot done by a parent at home rather than going to the doctor or lab for a blood draw. 
• Budget and the possibility of ordering add-ons with the same company. Food sensitivity testing can be expensive, and it can be best to bundle tests together for cost savings. 
• Ensure immunity is strong enough to test. If a test comes back with negative results multiple times, the child may not be mounting enough of an immune response. IgG, IgA, and IgM can be measured to assess overall immune response.
• Is the child currently eating the food that is being tested? Expect results only for foods eaten regularly. 
• Not all food sensitivity testing is equal. Companies can vary in method and reproducibility and the standards used in the clinical lab facility. All food sensitivity testing on Rupa Health’s portal is verified by 3rd party CLIA.

Overall, IgG blood testing is the most common food sensitivity test ordered. A more involved food sensitivity test might include IgG in addition to some of the following:

• IgA and secretory IgA (SIgA) antibody testing provide additional information about foods that may be causing mucosal damage (ex., anti-gliadin).
• Cd3 Complement activation has been researched in association with food-related inflammatory conditions. Testing for IgG with C3d complement protein aims to provide an additional layer of sensitivity and specificity for more accurate results than IgG alone. 
• IgG4 A study measuring the IgG4 antibody levels in certain foods showed that patients experienced significant improvement after three months of food elimination of the reactive foods. 
• Zonulin Higher than normal levels of zonulin, a biomarker of intestinal permeability, is an indicator of a leaky gut. 
• Cytotoxicity testing Another category of food sensitivity testing that does not fall under the umbrella of IgG-based testing is cytotoxicity testing. The ALCAT (antigen leukocyte cellular antibody test), MRT (mediator release testing), and LRA (lymphocyte response assay) each use different methods to stimulate white blood cells and observe reactions to food. 

Common Food Sensitivity Tests for Kids

KBMO Diagnostics FIT test (blood spot or serum) evaluates sensitivities of up to 176 foods and additives and measures both IgG and C3d. As of May 2022, the FIT 132 and 176 tests will include a new zonulin assay and both IgA and IgG for zonulin, occludin, and candida. Individualized 7 Day meal plans based on the FIT Test results are provided, as well as a mobile app with the list of food sensitivities which is very user (and kid) friendly. 

The Basic Food Sensitivity Panel by Ayumetrix measures IgA and IgG antibodies of up to 96 commonly consumed food antigens. Pricing for specific combinations can vary depending on other add-ons, such as zonulin.

Immune Reactivity Screening

Cyrex Array 10 (serum) measures reactivity of up to 180 food antigens. This lab tests for reactions to foods in cooked, raw, and modified foods, food enzymes, lectins, and artificial food additives, including meat glue, colorings, and gums, which is unique to Cyrex labs. In one study, IgG, IgA, and IgM antibodies against modified food antigens were found at much higher levels than antibody reactions against raw food antigens.

Wheat/Gluten Reactivity Tests

Cyrex Array 3X  (serum) assists in the identification of wheat reactivity, non-celiac gluten sensitivity, celiac disease, intestinal barrier damage, and wheat-related autoimmunity.

Gluten-Associated Cross-Reactive Foods 

Cyrex Array 4 (serum) identifies reactivity to foods known to cross-react with gliadin and can be used to identify possible reactions to newly introduced foods on a gluten-free diet.

Total Immunoglobulins (Immunoglobulins G,A,M)

Cyrex has the option to add on Total Immunoglobulins (GAM) at no cost. Please note you must do a serum blood draw to choose this option. This assesses the overall production of Immunoglobulins G, A, and M in the body and can be used to indicate general immunity. A sufficient immune response is necessary for accurate results on a food sensitivity panel. 

Intestinal Permeability 

Cyrex Array 2 (serum) measures intestinal permeability to large molecules and identifies the damaging route through the intestinal barrier. Cyrex's panel assesses gut barrier damage by measuring antibodies to barrier proteins. This includes measuring antibodies against the tight junction proteins (zonulin and occludin) and antibodies to the actomyosin network, which maintains the plasticity of tight junctions. It can detect barrier damage before dysregulation in absorptive function, allowing for early detection and intervention. This test can also monitor the progress of an intestinal repair protocol.

Comprehensive Stool Test

Pairing a comprehensive stool test and a food sensitivity panel can provide a complete picture of a child's overall gut microbiome and help determine the root cause(s) of symptoms. The GI-Map detects a microbial imbalance, microbes contributing to illness, and indicators of digestion, absorption, inflammation, and immune function- all important factors in a child's gut health. Zonulin, the marker for leaky gut, can also be added to this test if it was not included in a food sensitivity panel. Calprotectin, secretory IgA (SIgA), and anti-gliadin SIgA are helpful markers on the GI Map that can reflect inflammation and immune response. 

Functional Medicine Treatment for Food Sensitivities in Kids

Based on the food sensitivity results, highly reactive foods would be removed from the child's diet for at least three months. After three months, a retest of food sensitivities and zonulin can be done, and the restricted food list should be modified based on the results. This can allow a greater variety of foods if the gut has healed to some degree. As an alternative, the diet can be continued for six months without reintroducing foods and retesting initiated at that point. 

When reintroducing foods, challenge one food at a time. The child would eat a significant amount of that one food over the course of a day, and any adverse reactions would be observed over the next 72 hours. If no symptoms are present, the tested food can be added back into the diet rotationally. If sensitivity does occur, that food should be placed back on the restricted list for three months and challenged again at a later time. 

Most children will be able to reintroduce many foods after the gut is healed. A 5-R approach (Remove, Replace, Reinoculate, Repair, Rebalance) can be used to reintroduce foods and observe reactions. If a child is tested for gluten sensitivity and cross-reactive foods and is reactive, gluten and any cross-reactive foods would ideally be avoided for the long-term and not reintroduced due to the more serious nature of possible autoimmune reactions.

In addition to removing any food sensitivities, it is helpful to consider limiting or eliminating other foods in the diet that are inflammatory and can contribute to a leaky gut. Replacing these inflammatory foods with an anti-inflammatory and Mediterranean-based diet can benefit a child's overall gut health and immunity. 

Modifying a child's diet can feel very overwhelming; some kids are picky or have certain comfort foods. In addition, elimination diets can be challenging because they must be followed 100% of the time to be successful. Fortunately, we currently have various options for testing food sensitivities, so a complete elimination diet is unnecessary. 

Many more food options, including a selection of gluten-free and allergen-free foods, are available now compared to the past. Trained practitioners can provide food lists for grocery shopping, individualized menus, recipe ideas, and supplement protocols to help a child succeed in following the diet and allow the gut to heal properly. It's also essential for parents to set the example and not eat eliminated foods in front of their children. 

Low Inflammatory Kid-Friendly Foods

Start with small healthy changes such as a smoothie made with fruit, almond milk, and baby spinach or nuts with fruit for a snack, and over time encourage more foods from the below list. Include these foods as much as possible (if they are not on the child's elimination list):

• Green leafy vegetables, such as spinach, kale, and collards
• Nuts like almonds and walnuts
• Fatty fish like salmon, mackerel, tuna, and sardines
• Fruits such as strawberries, blueberries, cherries, and oranges

Summary

Food sensitivities do not occur in isolation and are part of a bigger picture for a child's gut health and immune system. Many people explore food sensitivity testing to alleviate obvious physical symptoms that could be related to adverse reactions to food, like rashes or GI symptoms. The underlying mechanisms of inflammation, immunity, and leaky gut have been implicated in food reactions. All of these, if dysregulated, can lead to more serious health conditions, including playing a significant role in the increasing prevalence of autoimmune diseases. We know that an individual's genetics plays a part in disease risk, but lifestyle, environment, and diet trigger the response, making these risks preventable. 

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