Sunday, May 11, 2014

Food Allergies vs Food Intolerances

There is often confusion between food allergies and food intolerances/sensitivities.  In this article I will explain what they each mean and help you decide if you should get tested for them.

Our bodies make several different immunoglobulins (Ig), also known as antibodies, which bind to microbes in order to neutralize them or tag them for other immune cells to deal with.
A food allergy is when the body has an immune response to a food protein.  This reaction is due to the immunoglobulin IgE. A food intolerance can be the immune response of the immunoglobulin IgG or sometimes a lack of certain enzymes needed to properly digest food.  An IgG reaction is also an immune response to a food protein, but the term ‘food allergy’ is reserved for IgE reactions.

Food Allergies
IgE attacks parasitic worms when they are present in our bodies and also binds to allergens to produce histamine.  IgE causes an immediate reaction in the body (usually in less than 2 hours) and can be in the form of asthma, hives, skin rash, headache or anaphylaxis.[i]  The most commonly talked about IgE reactions are those to peanuts and bees, but people can

have reactions to all sorts of substances including medications, dust mites, seafood, grass and pollen.  The most common test for this is a skin prick test where small scratches are made on the skin and small amounts of different allergens are applied.  This gives results in 10-20 minutes so they can be discussed immediately.  People are often able to self-diagnose food allergies due to the immediacy of the reaction.  One theory explaining the rise in food allergies is that we are not often exposed to worms leaving IgE with nothing to do.

Food Intolerance
IgG is the main immunoglobulin in the body and protects the body against viruses, bacteria and fungi.  IgG is the only immunoglobulin that passes the placental barrier providing protection to the fetus and also passes into breast milk along with IgA.  Measurement of IgG is used to check for immunity to some viruses such as measles, mumps and chicken pox. 

Unfortunately IgG can also react to foods if there is inflammation in the bowel allowing small particles of undigested food to pass through.  This can present as a variety of symptoms including headaches, fatigue, irritable bowel syndrome, depression, arthritis, chronic respiratory problems, weight problems, anxiety, insomnia and migraines.i [ii] IgG reactions are often delayed and can last for weeks or months after ingestion of the problem food. i Given this and the large variety of symptoms it can cause, it can be difficult to diagnose this reaction.  Common IgG reactions are to wheat, gluten, dairy and soy.  The common test for IgG reactions is an easy finger prick blood test.

If you think you may have food allergies or intolerances it is important to see your naturopath or other health care provider to ascertain the problem foods or substances so they can be avoided and you can begin the journey to better health.

[i] Cooking for the low reactive (elimination) diet.  Vivienne Saville, ND. Aug 2006, Darwin.  Published by Recipe To Health

[ii] Food Detective (Internet). (cited 2014 Mar 3). Available from: