Common food allergens such as nuts, eggs, dairy and wheat are arranged on a white board. The photo is taken looking down on them.

Australia has one of the highest rates of allergies in the world, but what is the difference between a food allergy and a food intolerance? CARA BOATSWAIN investigates.

The free-from movement has certainly helped grow awareness of food allergies and intolerances, but many still mistakenly believe the terms are interchangeable. With one resulting in possible life-threatening reactions, the importance of understanding the difference is enormous.


“A food allergy is an immune system response to a food protein that, for most people, is actually a healthy nutritious food,” explains Maria Said, CEO of Allergy and Anaphylaxis Australia. “The immune system, for some reason, sees the food as a threat and the reaction that takes place can be mild for some, but for others, potentially life-threatening.”


The immune system can respond differently to allergens, which is why there are different types of food allergies.


IgE mediated food allergies cause the immune system to react abnormally when exposed to a specific food.

Reaction happens fast (usually within two hours of eating the food) and is the result of the immune system producing an allergen-specific antibody, immunoglobulin E (IgE), in response to proteins contained in the allergen.

This type of food allergy is more common in children than adults and only a small amount of the allergen is needed to trigger a reaction. Anaphylactic responses to food are usually a result of an IgE mediated food allergy.


In Australia the most common causes of IgE mediated food allergies are:

• cow’s milk
• egg
• peanut
• other tree nuts
• seafood
• wheat
• soy

While over 90 percent of food allergic reactions in Australia are caused by the above foods, the list isn’t definitive. Any food could cause an allergic reaction.

The good news is that around 80 percent of children grow out of allergies to milk and egg. Wheat and soy allergies are also less likely to persist into adulthood. Unfortunately, nut and seafood allergies tend to continue into adult life.

14 different food allergens as illustrations to show food allergy vs food intolerance.
When a person with a food allergy eats the food they are allergic to, their immune system triggers an allergic reaction, which can range from mild symptoms such as hives and swelling, to more severe symptoms such as difficulty breathing, swelling of the tongue and persistent dizziness.


Allergic reactions to food fall into two categories: mild to moderate and severe, the latter can be a sign of an anaphylactic reaction.

Mild to moderate symptoms include:

• swelling of the face, lips and/or eyes
• hives or welts on the skin
• abdominal pain and/or vomiting
• eczema or rashes
• tingling mouth

Severe (anaphylactic) reactions include:

• difficult/noisy breathing
• swelling of the tongue
• swelling/tightness in the throat
• difficulty talking and/or hoarse voice
• wheeze or persistent cough
• persistent dizziness and/or collapse
• pale and floppy (in young children)


The Australian Society of Clinical Immunology and Allergy (ASCIA) warn that allergy tests alone are not sufficient to diagnose an IgE mediated food allergy. The three steps recommended by ASCIA are:-

a) consultation with medical practitioner detailing medical history
b) tests to identify IgE sensitisation to an allergy with results interpreted by a clinical immunology/allergy specialist
c) supervised oral food allergen challenge, if required

Allergy testing can show if a patient has (or hasn’t) been sensitised to an allergen. If not sensitised it means that an
IgE mediated reaction is unlikely. Unfortunately, allergy tests can not show how severe a response to a sensitised food will be.


Non-IgE mediated food allergies are caused by a reaction involving other components of the immune system apart from IgE antibodies. The reactions do not appear immediately after the consumption of the food. In fact, it can take up to 24 hours for symptoms to appear.

Non-IgE mediated food allergies are not as well understood as IgE mediated food allergies. The delay between consumption and reaction can make it more difficult to make the connection between the offending food and the symptoms.


The most common foods for non-IgE mediated food allergies are:

• cow’s milk (infants)
• soy proteins (infants)
• wheat (older children)


Non-IgE mediated food allergies do not result in anaphylaxis, so they are rarely life-threatening.

Symptoms are usually experienced in the gastrointestinal tract or on the skin. They include:-
• delayed eczema
• delayed vomiting and diarrhoea
• loose, frequent bowel actions
• blood or mucus in stools;
• irritability and unsettledness in infants


Diagnosing non-IgE mediated food allergies can be difficult. A lack of easily accessible blood or skin tests combined with the delayed reaction time doesn’t make the task any easier. An elimination and re-challenge diet is required to diagnose a non-IgE mediated food allergy. The process can take months to complete properly as usually only one food type is removed at a time.

Restricted diets can interfere with other diagnostic tests(such as the need to consume gluten while being tested for coeliac disease) and can lead to nutritional deficiencies. For these reasons it is very important that the elimination diet is undertaken with the support and supervision of a medical practitioner and dietitian.

For more information on allergy testing visit the ASCIA website (


It is also possible to experience a mix of IgE and non-IgE mediated symptoms and signs. This is often seen in children with a cow’s milk allergy.


Food intolerances involve the digestive system and with the exception of sulphite and benzoate reactions, they do not cause anaphylaxis (severe reactions), that can be life threatening. Instead they are caused by reactions to food chemicals that irritate the nerve endings in different parts of the body.


Food chemicals can be found in many different foods and the response can differ from person to person. Some people are born more sensitive to food chemicals than others, but environmental triggers like changes to your diet or a nasty bout of gastro can alter the way your body reacts to food.

The food chemicals most commonly linked to food intolerance are:

• salicylates – found in many fruits, vegetables, herbs and spices, honey, tea, coffee, beer and wines

Tomatoes are high in salicylates and glutamate. These two nutrients are common food intolerances.

• amines – found in banana, avocado, tomato, cheese, chocolate, wine and other fermented foods

• glutamate – found in tomato, cheese and stock cubes

Parmesan cheese is considered to have high levels of glutamate, which is a type of amino acid that acts as a natural flavor enhancer.

• preservatives – such as benzoates, nitrates and sulfites


There are a number of variables when it comes to food intolerance symptoms and reactions. The chemical you’re sensitive to, the degree of your sensitivity and how much of that chemical you consume in a day can all impact your response.

The time it takes for symptoms to develop can also vary with food intolerances. Some people see signs immediately, while for other is can take 12 to 24 hours.

The most common symptoms are:

• gastrointestinal issues
• nausea
• headaches
• recurrent hives and swelling
• reflux
• flu-like aches and pains

Unlike a food allergy, where the consumption of even the tiniest amount of an allergen can product a reaction, food intolerances are dose dependent.

A small amount of a chemical-rich food may not produce a reaction, but larger amounts that exceed your dose threshold can. Food chemicals can also build-up in the body, so eating small amounts regularly is not recommended.


As there is no immune response involved in a food intolerance diagnosis can be tricky. “Food intolerances do not show up on allergy testing,” explains Said. “It can be a difficult concept to understand, as doctors also poorly understand intolerances.”

There is no reliable skin prick or blood test to diagnose a food intolerance. Food intolerances are diagnosed based on medical history and response to food elimination tests.

The best approach is to first see your doctor to:

• check for other conditions that may be causing symptoms.
• determine if diet is causing your symptoms.
• identify individual triggers to be avoided.


With similar symptoms and both requiring a food elimination diet for diagnosis, it’s understandable if you’re confused about the difference between a FODMAP sensitivity and food intolerance. However, the underlying cause of these conditions is very different.

FODMAPs (Fermentable Oligosaccharides, Disaccharides,Monosaccharides and Polyols) are a group of short-chain carbohydrates and sugar alcohols commonly found in the foods we eat. These carbohydrates are poorly absorbed in the intestine by some people and result in a range of gastrointestinal symptoms.

Studies have shown that people with irritable bowel syndrome (IBS) show an increased sensitivity to FODMAPs. 76 percent of people with IBS have reported an improvement in symptoms after following a low FODMAP diet.


FODMAPS can be found in many different foods, many of which are also high in food chemicals. While space constraints prevent us from listing all of the foods containing FODMAPs here are some those most commonly consumed:-

• oligosaccharides – wheat, rye, onions, artichokes, asparagus, leek, beetroot, legumes, beans, lentils, chickpeas, cabbage and Brussels sprouts.

Legumes, beans, lentils and chickpeas all contain oligosaccharides, the ‘O’ in FODMAP.

• lactose – milk, ice cream, yoghurt, custard, dairy desserts, condensed and evaporated milk, milk powder, margarine and cottage, ricotta and cream cheeses. Lactose is represented by the “D” in FODMAP,for disaccharide (sugar).

• fructose – honey, apples, mangoes, watermelon, prunes, figs and high fructose corn syrup.

Honey contains fructose, the ‘F’ in FODMAP. It is a common sweetener it processed

• polyols – apples, avocado, mushrooms, cherries, lychees, nectarines, pears, plums, sorbitol, mannitol, xylitol, maltitol and isomalt.


Like a food intolerance, symptoms associated with a FODMAP sensitivity vary from person to person. Common
symptoms include:-

• bloating
• diarrhoea
• flatulence
• abdominal pain
• constipation


There is no test to definitely diagnose IBS. Doctors will review your medical history and conduct tests to rule out other conditions before looking at IBS.

If a low FODMAP diet is recommended you will need to follow an elimination diet to identify your food triggers. It is recommended that this is conducted under the guidance of a FODMAP-trained dietitian.

The FODMAPs that are triggers for one person, will be different to those that trigger symptoms in others. It’s definitely not a one size-fits-all approach.

It’s also important to remember that it’s a low FODMAP diet, not a no FODMAP diet. Once your triggers have been identified, you’ll be able to introduce FODMAP-containing foods that you don’t react to. This is important to ensure you are eating a balanced diet.

For more information about the low FODMAP diet and to try some delicious recipes, visit our sister publisher FODMAPPER.


If you are experiencing any of the above symptoms you may be wondering what to do next. First, make an appointment to see a medical professional before eliminating any foods from your diet. As previously mentioned, certain tests, like the test for coeliac disease, require you to regularly consume the allergen (eg.gluten/wheat), for the test to provide accurate results.

You could also start a food and symptom diary. This can be a helpful way to identify the foods you may be reacting to.

In a notebook, rule up the following columns:-

• time that you ate
• food or beverage consumed
• quantity
• symptoms experienced
• time you noticed/experienced symptoms

Each time you eat, write a response in each column. In the symptom category you might find it helpful to also rate the severity of the symptoms you’re experiencing using a scale of one to 10.

A food and symptom diary can be a helpful way to identify the foods you may be reacting to.

Your health professional may have a different diary system that you’ll need to adopt after your consultation, but in the meantime this will help you identify patterns and possible triggers to discuss with them.