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Food Sensitivities/Intolerance

This information is has been researched from a variety of resources believed to be trustworthy and based on scientific research. It is provided only as a resource and is not intended as medical advice or endorsement. If you believe that you have a food allergy or intolerance, it is very important to discuss your concerns with a medical professional.


Is it a Food Allergy, Sensitivity or Intolerance?

Sometimes people believe that they have a food allergy because they are experiencing symptoms after eating but it is actually a food intolerance or sensitivity.  The difference is that food allergies involve the immune system and affect many organs in the body and food sensitivities and intolerances do not. With food allergies, complete avoidance is necessary but small amounts of the food may be possible with food sensitivities and intolerances.

This does not mean that food sensitivities and intolerance are imaginary; they are very real and can have symptoms very similar to allergies.  Food sensitivities and intolerances are actually more common than food allergies.

Food intolerance is a mechanism by which the digestive system cannot properly break down a food that has been eaten. 

Food sensitivity differs from food intolerance in that symptoms can affect more than the digestive system and may not be immediately apparent after ingesting the offending food.

Lactose Intolerance

The most common food intolerance is lactose intolerance, sometimes called lactose deficiency.

With lactose intolerance, there is not enough of the enzyme lactase in the small intestine.  Without lactase, the body cannot break down the sugar lactose that is in all dairy products to a varying degree.  You can be born with lactose intolerance or it can develop naturally as we age or due to an illness or injury (such as Celiac Disease).

Symptoms of lactose intolerance include:  nausea, sometimes with vomiting; gas, cramping or bloating; and diarrhea.  Usually these symptoms present themselves between 30 minutes and 2 hours after ingesting dairy products and are normally not severe.

If your doctor diagnoses you with lactose intolerance, you will then limit your consumption of dairy products, limit those items with higher amounts of lactose, take a lactase enzyme supplement when planning to ingest dairy products and/or eat dairy products that are specially formulated and labelled as lactose free.

Fructose Intolerance

Not as well known as lactose intolerance, fructose intolerance is the body’s inability to break down the sugar fructose.  Fructose is naturally found in fruits and honey, is the main component of table sugar and is added as an ingredient to numerous processed foods under a variety of names.

Fructose intolerance is caused either by an inherited disorder where the enzyme to break down fructose is not present or from fructose malabsorption.  The inherited disorder is very serious and can cause liver and kidney damage.  Malabsorption does not cause liver or kidney damage but gastrointestinal symptoms such as diarrhea, bloating, gas and abdominal pain.

Complete avoidance of fructose, sucrose and sorbitol is the current treatment.

Non-Celiac Gluten Sensitivity and FODMAPs

Sometimes referred to as gluten intolerance or NCGS, until recently, this sensitivity was not well accepted in the scientific community, primarily because there is no way to definitively diagnose it.  Gluten sensitivity is not Celiac Disease.

However, recent research by The Center for Celiac Research and Treatment in Boston shows that in addition to the approximately 1% of North Americans who have Celiac Disease, there are an additional 6% of Americans who have gluten sensitivity.  That works out to approximately 18 million Americans.

Gluten sensitivity affects a number of body systems with a wide variety of symptoms such as:  diarrhea, constipation, abdominal pain, bloating, gas, headaches, fatigue, “foggy brain”, depression, joint pain and ADHD like behavior.  Gluten sensitivity can only be diagnosed after a medical professional rules out Celiac Disease, Irritable Bowel Syndrome, and other potential diseases depending on your symptoms.

Until recently, the only treatment known at this time is complete avoidance of the gluten containing grains of wheat, barley, rye and their subspecies.  However, after research conducted at Monash University in Australia, it's believed that people suffering from NCGS and/or IBS may actually be reacting to far more than gluten.  Instead, they may be reacting to sugars in a wide variety of foods known as Fermentable Oligosaccharides, Disaccharides, Monosaccharides And Polyols.  These substances are shortened to the acronym FODMAPs.  These FODMAPs are found in everything from milk to certain fruits, mushrooms and high fibre grains, including inulin.  A low FODMAP temporary diet refraining from these food sources high in FODMAPs may offer relief.  For more on FODMAPs, check out the Monash University research and diet.

Chemical Sensitivity

A wide variety of people report symptoms to specific chemical compounds found both in nature and man made.  With the exception of the preservative sulfur dioxide (see below), reactions to chemicals are sensitivities because the symptoms affect a wide range of body systems but do not engage the immune system.

Like other sensitivities, symptoms can affect a number of body systems but are more typically presented as non-specific symptoms such as headaches, fatigue, hay fever/asthma, burning mucous membranes, and decreased lung function.  While there is no test for chemical sensitivities, a trusted medical professional can work with you to help minimize your symptoms.

Building related illness is generally a medically accepted syndrome if more than 1 person occupying the building has documented symptoms.  If you believe that your symptoms are caused by a building you live or work in, testing can be done in the building for air quality.


Because chemicals have no protein, the body does not respond to them as an allergen with a histamine response with the exception of the group of preservatives known as sulphites.  Although sulphites do not have protein in them, there are documented cases of major anaphylactic allergic reactions to them.  The reason for this is not understood.  There are also documented cases of severe asthma attacks triggered by the ingestion or inhalation of sulphites.

In Canada, sulphites must be labelled when food items have concentrations of over 10 parts per million (ppm).  There are some exceptions to this rule including the use of sulphites on fresh cut or shredded potatoes.  Fermented products may also naturally create sulphites such as with wine.  Most wine makers add sulphites during the process but even organic wines will have sulphites in them naturally from the fermentation process.  Sulphites may also be added to medications.

While rare, people with a food allergy to sulphites and those with major sulphite sensitivities may also find that they react to the sulfur compounds found naturally in a variety of fruits and vegetables.