Food allergy vs intolerance explained

We can all remember an occasion where we’ve eaten something that didn’t agree with us – that packet-mix cake from our childhood, say, or greasy takeout on a road trip.

However, if your day to day diet causes you discomfort or pain there could be something else going on. There’s a chance you might have a food allergy or intolerance, which if left untreated can have serious health risks.

And you wouldn’t be alone. Australia has one of the highest allergy rates in the world with 1 in 10 infants and 2 in 100 adults being affected by a food allergy. Although allergies are much more common among infants, many of these will be outgrown. Food intolerance is even more common than food allergy.

Both can be unpleasant, complicated and in some cases life-threatening. The good news is, they can be effectively managed!

What’s the difference between a food allergy and intolerance?

A food intolerance involves the digestive system and is usually the result of an inability to process or digest certain foods. This could be due to an enzyme deficiency, gastrointestinal disorder (e.g. IBS), sensitivity to food additives or reaction to naturally occurring food chemicals. Although food intolerances can cause discomfort, they are not life threatening. Some people may even be able to eat the problem food in small amounts without experiencing any symptoms.

A food allergy, on the other hand, involves the immune system. The severity of an allergy can vary from person to person with some being much more sensitive than others. Unlike an intolerance, a food allergy can cause a serious, potentially life-threatening, reaction if even a microscopic amount of the food is eaten, touches the inside of the mouth or is inhaled.

Signs & symptoms of a food allergy

Allergic reactions can occur very quickly, usually within 20 minutes to 2 hours after eating or coming in contact with the food.

Signs & symptoms of a food intolerance

These usually show anywhere between 30 minutes and 48 hours after consuming the food, which complicates the identification of the problem foods.

Most common food allergens among adults

Although you can develop an allergy to almost any food, the most common food allergies we see in adults are to:

Most common food intolerances among adults

There are many food substances people can have an intolerance to, each of which are found in a variety of foods. The most common include:

Food substance

Example foods


Milk, Milo, chocolate, ice cream, cheese, yoghurt, cream


Barley, rye, oats, wheat

Preservatives (e.g., sulphites)

Cordials, dried fruit, sausages, wine


Fruit, vegetables, herbs, spices, tea, honey


Cheese, chocolate, bananas, avocado


Coffee, chocolate, energy drinks, tea, soft drinks


Wheat, rye, onions, garlic, legumes, lactose, honey, apples

Can I develop a food allergy or intolerance at any age?

Most food allergies appear in childhood, but they can develop at any time. It’s possible to develop an allergy to foods you’ve eaten for years with no problems.

Food intolerances generally occur later in life. This is because as you age digestion naturally becomes slower and your body produces less of the enzymes needed to break down food. You may also become more sensitive to a particular chemical or food additive – for instance, sulphites.

Testing for food allergy or intolerance

If you are concerned you may have a food allergy or intolerance, it’s important you seek a proper diagnosis from a qualified medical practitioner. Your practitioner can test you for allergies with a simple blood test or skin prick test. If these show you are allergic to a particular food, you can eliminate the food from your diet to avoid any reactions.

If allergy testing comes back negative, it’s possible you have a food intolerance.

Beware of anyone offering intolerance testing! Unfortunately, most of these tests (except for a specific breath test for lactose intolerance) lack both scientific evidence and clinical relevance.

Diagnosing and managing food intolerance requires the input and supervision of a qualified health professional, such as your dietitian. We would recommend you first keep a food diary and note down any symptoms which may be related to food. Then you will need to eliminate all suspect foods from the diet before reintroducing them one by one, to see which food(s) or food substance(s) cause your symptoms. Your dietitian will then be able to assist you in finding your tolerance threshold(s) and creating a personalised diet.

Bottom line

Whilst food allergies and intolerances are often confused, the two are very different. They can both negatively impact your health and should be taken seriously. If you suspect you may be allergic or intolerant to a certain food, speak to your doctor or dietitian about testing and management.

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