Understanding food sensitivity testing and how it differs from food allergies and food intolerances

Brittany SchamerhornFeatured, Food Allergies, Food Intolerances, Food Sensitivity Testing

It is no secret that diet plays a huge part in our health and how our body functions.  There are many people who avoid or add in certain foods in order to improve their health and wellbeing. When asking people why they are avoiding certain foods the usual response is that they are ‘allergic’ to it. However, I would argue that this word is often misused due to a lack of understanding.

There are three main reasons why an individual would avoid a certain food item: food allergy, food intolerance, and/or food sensitivity. Though all three may sound similar, and thus often be used interchangeably, their mechanism and how they affect the body are very different. A better understanding of these three mechanisms and their differences is key to understanding the processes occurring in the body and properly interpreting and managing symptoms.

Enzyme deficiency Immune (IgE) response Immune (IgG) response
Shortly after consumption Immediate Symptoms can be immediate or delayed (hours – days)
Digestive disturbances (pain, gas, diarrhea) Itchiness, swelling, redness, cough, nausea and vomiting.

Difficulty breathing, shock, and loss of consciousness are signs of a life threatening allergy

Type of reactions can vary: eczema, migraines, bloating, digestive disturbances, mental function, inflammation
Will occur every time food is consumed Will occur every time food is consumed May or may not occur every time food is consumed

To start, let’s separate them into two simple categories; digestion-based or immune- based. Digestion-based responses occur when the body is physically unable to break down/digest a certain food item due to insufficient materials. Immune-based responses occur when our bodies’ immune system for some reason is reacting to the food we eat.

Food allergies and food sensitivities are both due to immune responses where the body is recognizing part of the food as dangerous and mounts a response. The key difference to these is the type of antibody that is responding to the food. Antibodies are produced by our immune system and are constantly around in an attempt to properly identify, react to, and protect our body from anything foreign that could be dangerous (for example viruses and bacteria). Sometimes the immune system gets confused and makes antibodies that view its own body/cells as dangerous and thus an autoimmune disease is present – but that’s another topic for another post.

Food Intolerence occurs due to a digestive insufficiency and results in digestive disturbances that occur soon after consumption. Usually, the insufficiency is the lack of an enzyme, meaning that the body is missing a key component in breaking down the food. The most common food intolerance is lactose intolerance that is due to a lack of the enzyme lactase. Lactose, a protein found in dairy products, needs to be broken down by lactase in order to be properly digested. In those lacking this enzyme, gastric upset (pain, gas, diarrhea, etc) will occur when they consume dairy. For some taking the enzyme via a pill (ex. lactase pills), it will allow them to enjoy the food symptom free.

Food Intolerance Testing

Food intolerance is largely determined based on history with predictable and repeated symptoms occurring after consumption of the food type.

Food Allegies are due to the IgE antibody. When this IgE antibody comes in contact with the food it reacts immediately. IgE antibody levels elevate quickly and symptoms can be seen very shortly after ingestion. Food allergy responses can range from uncomfortable to life threatening. Common symptoms are: feeling itchy (can occur in the mouth, throat and the surface of the skin), swelling, redness, cough, nausea and vomiting. Difficulty breathing and shortness of breath can occur due to closure of the airway. Shock and loss of consciousness can also occur.

IgE antibody levels will drop quickly and patients are usually symptom free within a week. Someone with a food allergy will always have a reaction upon consumption of the aggravating food. This repeated and predictable response is specific to food allergies.

The most common foods that cause a food allergy are: eggs, milk, peanuts, soy, fish shellfish, tree nuts, and wheat.

Food Allergy Testing

Like food intolerances, allergies are also largely determined based on history with predictable and repeated symptoms occurring after consumption of the offending food. Blood IgE levels can be tested during an attack to confirm an allergy. A scratch test can also be done to determine IgE responses to both environmental and food allergens.

Food Sensitivities are due to the IgG antibody. IgG reacts much differently from IgE, resulting in a very different patient presentation. When the IgG antibody comes into contact with the food, the response is much slower. IgG antibodies slowly build up over time and result in non-typical symptoms that can differ from patient to patient. Since symptoms do not appear soon after ingestion and IgG food sensitivities depend on both dose and frequency, it is much harder to correlate foods to symptoms. These slow responses and the variation in symptoms make food sensitivities much harder to identify and diagnose!

Food Sensitivity Testing

Food sensitivities can be found in one of two ways: a blood test or elimination diet.

  • The elimination diet involves following a very strict restricted diet for an extended period of time, followed by slow introduction of foods (referred to as the challenge phase). Throughout both the elimination and challenge phase of the diet symptoms are carefully tracked to identify any correlation.
  • The blood test is an IgG food sensitivity panel. A sample of blood is taken and then challenged with various foods in the lab and the reactivity of the IgG antibodies is measured. The more reactivity present, the more likely a food sensitivity is present. Following this test, most doctors will then prescribe a specific elimination diet where foods with elevated reactivity are removed for an extended period of time. Like the elimination diet, symptoms are closely tracked and foods may be introduced back into the diet to confirm that sensitivity/response is present.

Food sensitivities may be the most frustrating diagnoses for a patient to understand. They are being asked to eliminate a food that they love and have not noticed any reaction to. However, usually after strict avoidance of the foods for an extended period of time, there is an improvement in the symptoms. In addition, patients may note more energy, less body aches, and more mental clarity – this could be due simply to an improvement in the diet but could also be due to the reduction of the IgG antibodies and the associated immune response.  For some patients after both elimination and treatment to improve the gut lining, the aggravating food can be tolerated and enjoyed again (usually in less regular and smaller portions).

There is not one universal diet that will be perfect for everyone. Determining which foods should be added/removed is part of the art of medicine and individualized care. Figuring out which diet is best for you can be a confusing, and at times frustrating journey, but better understanding which foods need to be avoided and why will help make the journey simpler!

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Brittany Schamerhorn

Brittany Schamerhorn is a fourth-year naturopathic medical student and clinical intern at BINM in Vancouver. She obtained her B.Sc from the University of British Columbia. By empowering patients with the right education and tools it is her goal to motivate and inspire patients to take control of their health and wellness allowing them to achieve their health goals and feel resilient again.  

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