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The 8 Most Common Signs Of A Food Sensitivity

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The 8 Most Common Signs Of A Food Sensitivity

Food sensitivities are extremely common and are on the rise. Recent studies show that our Standard American Diet and lifestyle can negatively affect the gut microbiome, causing inflammation and lower immunity.

Food sensitivities can be hard to diagnose due to their wide range of symptoms and can be delayed by up to 48 hours, making the offending food especially difficult to pinpoint. Because of this, food sensitivity testing has gained a lot of attention over the past few years.


Food Sensitivities vs. Food Allergies

It’s very important to understand that food sensitivities and food allergies are two very different diagnoses.

Food Allergies (IgE) cause an immediate histamine reaction within minutes to hours of ingested food, and these allergies can be life-threatening. Most people know that they have a food allergy, which is typically diagnosed at a younger age. Common food allergens are tree nuts, seafood, dairy, and eggs.

Food Sensitivities (IgG) are more common than food allergies and can cause delayed symptoms hours to days after a person has ingested the food. Food sensitivities are not life-threatening but do cause discomfort and, if left untreated, can lead to inflammation in the gut causing many other symptoms. Food sensitivities can be diagnosed at any age and can be remedied with proper nutritional guidance and gut healing protocols.  

Common Types of Food Sensitivity Testing

Immunoglobulin G (IgG):

IgG-specific antibody-mediated reactions are the body’s natural and normal defensive reactions to infiltrating food antigens. IgG food sensitivity has more published research compared to other food sensitivity tests and is the most common type of testing used.

Immunoglobulin G4 (IgG4):

A subclass of IgG testing. IgG4 indicates the presence of antibodies to foods that will not usually cause inflammation, even though high amounts of these antibodies indicate the presence of immune reactions against food antigens. Testing for IgG4 comes in handy for patients not currently showing any inflammatory reactions to foods.

Immunoglobulin A (IgA):

Found in mucous membranes, including the digestive tract. If IgA antibodies are elevated to a particular protein (antigen), this can indicate an immune response to mucosal irritation.

Food Sensitivity Signs & Symptoms

Food sensitivity symptoms can easily overlap with other common medical diagnoses. Therefore, it’s vital to rule these sensitivities out while looking for a root cause. The most common symptoms associated with food sensitivities are:

  • Unexplained loose stools or constipation
  • Gas, cramps, and bloating
  • Skin conditions (eczema, acne, psoriasis, and dermatitis
  • Headaches (not caused by tight muscles)
  • Brain Fog
  • Joint pain
  • Anxiety or Depression (due to the gut-brain connection)
  • Vitamin and mineral deficiencies (due to an inflamed small and large intestine)

Food Sensitivity Possible Causes

Stress and the Standard American Diet are two of the most common reasons for food sensitivities. They both play a role in disrupting the gut microbiome (good bacteria) and contribute to leaky gut syndrome.

What is Leaky Gut

A leaky gut is an unhealthy gut lining with microscopic cracks or holes, allowing partially digested food, toxins, and bacteria to penetrate the tissues beneath it. Once these larger food proteins are in the bloodstream, our immune system creates an inflammatory response to protect against these foreign invaders. Constant consumption of these trigger foods leads to food sensitivities causing an inflammatory response every time you consume that food.


Chronic stress is a significant risk factor for developing food sensitivities and is often overlooked. The gut-brain connection plays an essential role in overall gut health.  

Cortisol is released when we are stressed, and when released in high amounts it can decrease Secretory Immunoglobulin A (sIgA).

sIgA is an immune antibody found throughout our mucosal barriers. It is the first line of defense against bacteria, food residues, yeast, parasites, and viruses.

When sIgA is decreased, our mucosal first line of defense is reduced. This can begin to disrupt the integrity of our intestinal lining, causing leaky gut syndrome.

High Cortisol -> Lower sIgA -> Reduced mucosal defense -> Leaky Gut

The Standard American Diet (SAD)

The SAD diet is loaded with processed, high inflammatory “foods.” I quoted the word “foods” because most people aren’t even eating actual food anymore. Fillers, additives, processed oils, and food colors make up a majority of the meals that American’s eat. These “foods” are not recognized by the body and create an inflammatory response when they are consumed. The body starts to make antibodies to attack these foreign substances to protect you, but long-term consumption leads to GI inflammation, dysbiosis (unbalanced gut bacteria), and eventually leaky gut.

Functional Medicine Labs for Food Sensitivities

Food sensitivity symptoms can show up days after consumption. This is why it is vital to test, not guess which foods are causing your reactions. Most food sensitivity tests look at at least 96+ different foods, and I can tell you from first-hand experience that it’s usually not the food you expect it to be. I have seen patients react to spices, additives, animal proteins, and varying fruits and vegetables.

The reason behind this is once those holes are in your intestinal lining, multiple different food proteins can slip through, causing a reaction.

The Top 2 Most Common Food Sensitivity Test Ordered on Rupa Health

  • Alletess Medical Laboratory
  • Ayumetrix

I prefer to offer my patients a blood spot option for food sensitivity testing to increase patient compliance. They can complete the test from the comfort of their own home. Most labs also offer serum and whole blood testing as well.


Functional Medicine Treatment for Food Sensitivities: 4 Rs of Gut Healing

A therapeutic approach known as the 4 Rs is commonly prescribed to heal the gut. It’s important to note that healing your GI tract takes time and serious lifestyle adjustments. It’s best to start your gut healing journey when you are ready to commit to the healing process.


One of the first steps in addressing food sensitivity is eliminating the food or foods that are causing symptoms for a period of 3-6 months while addressing the other underlying factors. Research shows that it can take up to 6 months for the body to stop making antibodies against the food and longer depending on several other factors. It will most likely take you longer to stop producing IgG antibodies if you have a higher existing concentration and are not as strict with avoidance of foods.


The second step is to replace these foods with nutrients in the diet that help to reduce inflammation and optimize digestive health. It’s also essential to ensure that the patient has sufficient hydrochloric (stomach) acid and digestive enzymes to assist with breaking down the proteins, fats, and carbohydrates in the diet


The third step is to reinoculate the intestinal microbiota with beneficial bacteria. Probiotics and fermented foods are added to rebuild good gut bacteria.


A Functional Medicine Practitioner will most likely add in therapeutic grade supplements to help heal the gut lining. L-Glutamine, Zinc Carnosine, Curcumin, Vitamin D, Collagen, and Fiber have all been shown to help decrease intestinal permeability and help reduce inflammation.

Functional Medicine Approach to Food Sensitivity Reintroduction

Here’s the silver lining in all of this. You don’t have to avoid food sensitivities forever. Patients should avoid highly reactive foods for at least three months.  It’s essential to re-test and then re-introduce patients to their food sensitivities one by one once they show a significant clinical difference.

A typical reintroduction is one new food every three days to see if there is a delayed response. Typical food sensitivity responses will be unexplained digestive upset, headache, or skin condition reemerging.

Things to Keep in Mind

Food sensitivity tests don’t usually test for lactose intolerance or Celiac disease.

Most food sensitivity tests only test for sensitivities to the proteins in foods, and lactose is a sugar.

If you have an IgG response to dairy, this means you are sensitive to the proteins in milk (casein or whey protein), not the lactose (sugar).

If you want to test for lactose intolerance, a lactose hydrogen breath test or elimination of lactose are normally prescribed.

A Celiac diagnosis is complex and usually requires a combination of blood tests and other procedures. The antibodies traditionally tested for Celiac Disease are not the same antibodies measured in food sensitivity tests. We do have multiple different celiac disease tests on our Rupa Health platform.

Food sensitivities are commonly reintroduced after an elimination diet and most patients are able to handle them in small amounts after their immune system and gut has had time to heal.



Food Sensitivities are on the rise. But with proper testing and treatment, along with nutritional guidance and education, patients can regain their gut health and enjoy their favorite foods again.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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