Food allergies, sensitivities and intolerances: Same or different?

Food allergies, sensitivities and intolerances: Same or different?

It is becoming more and more common to hear that someone cannot eat a particular food because they are sensitive or allergic to it, while others may be having various symptoms and cannot quite figure out what the offending foods are. Reactions to foods may not be due to one type of mechanism but may be multiple mechanisms occurring simultaneously or individually.

Often the terms allergy, sensitivity and intolerance are used interchangeably, when in fact, they are not the same thing. These different types of reactions are immune-mediated or non-immune-mediated reactions.

Immune-mediated mechanisms

As Josh Gitalis (Functional Medicine Practitioner and Certified Nutritionist) writes, think of the immune system as law enforcement agents, where there are different branches and players that respond to different threats. For example, in Canada there are border police, RCMP, transport enforcement, sheriffs, park wardens, etc.; they all work for the same organization, but respond to different dangers or risks. Similarly in the immune system, there are different players reacting to different threats. Some of these immune system players are called immunoglobulins (Ig) and are given a letter to distinguish between them. There is immunoglobulin G (IgG), immunoglobulin E (IgE), immunoglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin D (IgD), where each of the different immunoglobulins is in charge of a different response. (Gitalis, J., 2016).

A true allergic reaction is one that is mediated by IgE (one of the types of immune responses). Allergic reactions are immediate (occurring within minutes to hours) and can be systemic, including potentially life-threatening anaphylaxis, or localized, such as hay fever, asthma, hives as well as vomiting or diarrhea. An example of a food allergy is a peanut or shellfish allergy. Often, referral to an allergist is recommended in the case of serious food allergies (ex. anaphylaxis, difficulty breathing).

Another type of immune-mediated reaction to food is an IgG reaction. This is known as a food sensitivity. This type of reaction is often confused with an IgE or allergic reaction, but it is different. IgG reactions are delayed, meaning they can take hours or days to develop. This often contributes to confusion in determining the food culprit of one’s symptoms. Food sensitivity symptoms are often varied and can include (but are not limited to): fatigue, skin rashes such as eczema and psoriasis, mood and memory disturbances, migraines, asthma, joint pain, weight gain, nausea, abdominal pain, bloating, gas, variations in stool type (diarrhea, constipation or alternating between constipation and diarrhea).

IgG food sensitivity testing is becoming an increasingly popular choice for many looking to determine what foods may be causing symptoms. There are many independent labs that offer food sensitivity testing, which can be accessed and performed by Naturopathic Doctors. Often, if you have a food sensitivity that shows up on an IgG test, it can indicate that you have “leaky gut syndrome” or intestinal hyperpermeability. Essentially, our digestive tracts are one tube from our mouth to our anus, and that tube has to properly control what passes through the lining of the intestines. When it becomes “leaky” allowing food particles to pass through that typically aren’t allowed to pass through, the food particles are recognized by our immune system and can cause the variety of symptoms (as mentioned above). This immune response is what is measured with testing. To help address the root cause, foods must be eliminated and the gut must be healed. (See article on leaky gut)

Conventional immunologists do not recognize the validity of these tests and often discount them as credible tests aimed at uncovering foods causing symptoms. This is because the tests are not standardized and each laboratory has their own methodology in determining food sensitivities, which is in contrast to standardized IgE testing. However, IgG food sensitivity testing can still be beneficial in determining what foods may be causing or contributing to one’s symptoms.

As an example from my own personal experience, after I completed an IgG food sensitivity test, I found out that I was sensitive to dairy. Once I eliminated dairy from my diet, I felt what it was like to no longer have digestive symptoms (bloating, gas, constipation) and my acne improved. Another example is of a patient who was about 10 years old at the time and had full body skin rash that wasn’t resolving with conventionally prescribed corticosteroid creams or would mildy improve then return once she stopped applying the cream. She did the food sensitivity test and found out she was sensitive to gluten. After avoiding gluten, her skin rash resolved.

Other patients have completed the food sensitivity test and their results haven’t been as remarkable or in some cases, there hasn’t been any improvement or any reaction to foods despite symptoms. This can occur because the reaction could be coming from a different component of the immune system other than IgG or because the reaction isn’t immune-mediated at all.

Non-immune-mediated mechanisms

After eating certain foods, some people experience symptoms that do not involve immune system mediated reactions. These non-immune reactions are called food intolerances. Similarly to food sensitivities, food intolerances can have a delayed onset of symptoms, as well as symptoms that vary, including digestive symptoms (bloating, gas, abdominal pain, nausea, vomiting, diarrhea), skin rashes, itching, headaches, fatigue, joint pain and restlessness to name a few.

Food intolerances can have a variety of different causes, which include:

  • Enzyme defects
    • Enzymes help with breaking down substances found in certain foods. If enzymes are faulty or low in supply, then the food will not be digested properly.
    • For example, in individuals with lactose intolerance, their body may either lack the enzyme (known as lactase) or have a faulty lactase enzyme required to break down lactose (type of sugar) found in dairy products. If not properly digested, lactose will not be absorbed and will be digested by naturally occurring bacteria in the digestive tract, causing symptoms of gas, cramping/pain, bloating and diarrhea.
  • Chemical
    • Some foods contain chemical substances that can have an affect on the body, where some people may be more sensitive to those chemical components than others and thus develop symptoms.
    • For example, a substance called methylxanthine found in coffee, chocolate, tea and cola can cause heart palpitations, restlessness and anxiety in some individuals. Another example is histamine-containing foods or foods that can develop a buildup of histamine, such as fish, cheese, sauerkraut. These can contribute to symptoms such as headaches, rashes, itching, diarrhea, vomiting and abdominal pain. Other chemical substances can include additives, preservatives and food colourings/dyes.
  • Toxic
    • Substances exerting a toxic effect can occur within a number of foods leading to symptoms.
    • For example, aflatoxin, a carcinogenic compound produced by certain molds/fungi, is found in peanuts, peanut butter and corn, amongst other foods. Though poisoning is relatively rare (and depends on various factors), symptoms of aflatoxin exposure include stunted growth and delayed development in children, liver damage, nausea, vomiting and abdominal pain, pulmonary edema (fluid buildup in the lungs), kidney and heart damage and convulsions.

Where to start?

It can be challenging to navigate the different types of food-related reactions that may be causing you symptoms. One of the best places to begin is by keeping a food journal/diary, tracking what you eat and what symptoms are experienced. Next, you might want to consider an elimination diet and/or testing. Naturopathic doctors can offer assistance in determining food-related reactions and which route to take to determine what’s contributing to your symptoms and how best to alleviate them.


Aflatoxin Could Be in Your Peanut Butter & More. (2016). Retrieved January 03, 2017, from

Aflatoxin Poisoning: Symptoms, Treatment & Effects. (n.d.). Retrieved January 03, 2017, from

Allergy or Intolerance? (2016, April). Retrieved January 03, 2017, from

Gitalis, J. (2016, October 03). What Are Food Allergies and Sensitivities? Retrieved January 03, 2017, from

IgG Food Sensitivity: Clinical Information for Professionals. (2014, January). Retrieved January 03, 2017, from

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