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Understanding Food Allergy and Intolerance






Modern day dining looks very different from the way it did in the 1970’s when my parents got dressed up in their best clothes to go out to dinner on a Saturday night. At the restaurant they pored over the menu offerings: French Onion Soup, Apricot Chicken, Waldorf salad, Quiche, Pasta Primavera and Black Forrest Torte. Missing from menus in the 70’s 80’s and even 90’s were the list of food allergens and the words “GF, DF, V, options available” that we expect to see on menus today.


Food allergies and intolerances have become increasingly prevalent in the last 30 years. While food allergy was defined around 150 years ago, records as far back as 2500BC show the understanding by ancient doctors that some foods could cause some people to experience adverse symptoms while not affecting others. In contrast, food intolerance is a modern concept that was defined in 1995 in order to differentiate between non-toxic, adverse reactions to food caused by food allergy and those which were caused by an alternative pathogenesis.


So, what is the difference between Food Allergy and Food Intolerance?

Put simply, food allergy involves the immune system while food intolerance involves the digestive system.


Food allergies are most likely to affect infants and children but also affect around 2% of Australian adults. The most common food allergens include: egg, cow's milk, peanut, tree nuts, sesame, soy, fish, shellfish and wheat.


In food allergies, as with environmental allergies, the immune system reacts to a substance (food protein) that is usually harmless. As a result, the immune system produces allergy antibodies known as Immunoglobulin E (IgE). These antibodies travel to the Mast Cells and cause them to release histamine. It is the release of histamine that causes the symptoms associated with an allergic reaction such as hives, swelling of the lips, eyes and face, itching in the mouth or throat, vomiting, or wheezing.

Allergic reactions may happen after exposure or ingestion of a tiny amount of allergen and occur quickly, usually within 30 minutes.


Other symptoms of food allergy that may seem a little more obscure include reflux, eczema, chronic diarrhea or failure to thrive in infants.


Anaphylaxis is a severe allergic response to a food allergen which requires medical attention and can be life threatening. For this reason, allergy testing should be performed where food allergy is suspected, especially in children.

Allergy testing may involve a blood test to identify allergen-specific IgE antibodies but the gold standard for allergy testing is skin prick testing.



Food Intolerances affect around 17% of Australians. Intolerances may be caused by naturally occurring substances in foods (lactose, fructose, salicylates, amines, caffeine, glutamate, FODMAPs etc) or by food additives (artificial colours, natural flavours, preservatives, flavour enhancers etc).


Food intolerance occurs when the body cannot digest or absorb a certain chemical or compound in the food. As a result gut bacteria may produce an excessive amount of gas or excess water may be drawn into the bowel, which leads to symptoms such as abdominal pain, bloating, constipation or diarrhea. Other symptoms of food intolerance may include nervousness, sweating, palpitations, headache, migraine, burning sensations/tightness on the skin, asthma-like symptoms and allergy-like symptoms.

The onset of these symptoms may present anywhere from a few hours to a couple of days after the food is consumed and may not occur every time the food is eaten. Symptoms of food intolerance are “dose responsive” meaning that the body can tolerate a certain amount of the food until the threshold is reached.


Food intolerances are diagnosed based on case history and elimination diet.


Long term, the digestive symptoms caused by food intolerance can disrupt the absorption of nutrients from foods, or cause avoidance of whole food groups, leading to deficiency of essential vitamins and minerals. The good news is that under a supervised elimination and challenge diet it is possible to identify which food chemicals are causing the intolerance so that whole food groups do not have to be avoided. In some cases food intolerances occur as a secondary condition, as a result of other factors disrupting the digestive system, and may be resolved through dietary changes and specific nutrient therapy.


Adverse reactions to food may also occur due to reasons other than allergy or intolerance.

If you are experiencing digestive issues or adverse reactions to food, book in for a free, 10 minute Discovery Call to find out how I may be able to help.

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