Home 5 Food Allergy 5 Differentiating between food allergies and intolerances

Differentiating between food allergies and intolerances

In season 2 of Friends, Ross accidentally eats kiwi. With his tongue swelling, he has to go to hospital urgently. Nearly 15 years later in the first season of The Big Bang Theory, Howard’s whole face swells after he eats a granola bar containing peanuts. Thankfully, he’s already in the Emergency Room at the time.

Other food issues may not be quite as obvious, though. Think of your colleague who can’t find the cause of her itchy skin or your uncle who’s prone to digestive difficulties.

Let’s take a closer look at food allergies and intolerances. As you’ll see, the key difference is whether or not your immune system is involved.

Immediate-onset food allergies

A typical food allergy is a sudden, severe or life-threatening allergic response to a certain food. It involves an overreaction from your immune system.

In our examples above, Ross and Howard both have classic type 1 food allergies. Their immune systems perceive kiwis and peanuts as a threat and produce specific IgE antibodies (immune globulins of the subclass E) in response. Those antibodies trigger an immediate allergic reaction to the food in question.

It’s very quickly clear that something is seriously wrong. Symptoms appear within minutes and may include:

  • Severe swelling
  • Tightening of the throat
  • Breathing difficulties
  • Itchy skin
  • Rash
  • Anaphylactic shock.

Foods that most commonly cause allergic reactions are:

  • Peanuts
  • Tree nuts
  • Milk
  • Eggs
  • Sesame seeds
  • Fish and shellfish
  • Soy
  • Wheat
  • Lupin (a legume found in a wide variety of foods).

It’s relatively easy to see the chain of cause and effect with type 1 food allergies because the reaction happens so quickly. Blood tests can confirm type 1 food allergies but may not really be needed.

What about a delayed food allergy?

A delayed food allergy involves your immune system but in a slightly different way. Your immune system produces IgG antibodies (immune globulins of the subclass G). These antibodies can lead to inflammatory processes.

But the symptoms don’t show immediately. There may be a delay of hours or days between eating the food and experiencing symptoms such as:

  • Constipation
  • Diarrhoea
  • Eczema
  • Flatulence
  • Irritable bowel syndrome.

As you can see, this sounds a little like a food intolerance. Indeed, many people refer to delayed food allergies as a food intolerance. But, scientifically speaking, it’s an allergy because it involves your immune system.

Food allergy type 1 Food allergy type 3 Food intolerance
Immune system involved?  Yes Yes No
Antibodies produced? Yes – IgE Yes – IgG N/A
Symptom onset Immediate Delayed Delayed
Symptoms Swelling
Breathing Problems
Digestive Digestive


What’s a food intolerance?

A typical food intolerance is when your body finds it hard to digest a certain food, usually due to an enzyme deficiency. Your immune system isn’t involved at all.

People with lactose intolerance, for example, can’t digest lactose, the sugar found in milk. Other people can’t digest fructose, the sugar found in certain fruits and vegetables.

Symptoms of a food intolerance usually start to show a few hours after eating the food, while it’s making its way through your digestive tract.

If you’re intolerant to a certain food, you may find you can eat small amounts of it without triggering any symptoms. However, if you’re allergic to it, you’ll need to avoid it completely.

Overcoming the confusion between delayed food allergies and food intolerances

Often, there’s a big difference between the way we talk about things in general conversation and their real scientific meaning.

You see this each winter when a colleague with a heavy cold describes it as ‘the flu’. Scientifically, these are two very different diseases but there are some overlapping symptoms.

It’s similar with a delayed food allergy and a food intolerance. In everyday conversation, someone with a delayed food allergy may often describe it as a food intolerance. After all, both conditions can lead to similar symptoms, usually experienced some time after you’ve eaten a trigger food.

But the underlying mechanism is different. One is an allergy because it involves your immune system. The other is an intolerance due to your inability to digest the food in question. Your immune system is not involved here.

Testing for delayed food allergies

The first step in dealing with a delayed food allergy is to identify the food that triggers it. In practice, this can be hard. When there’s a long delay between eating a food and experiencing symptoms, it’s very hard to know which food was the culprit.

That’s where ImuPro’s tests help. One quick test allows you to identify any delayed food allergies you may have. We only test on blood serum because this contains the highest concentration of IgG antibodies.

When you order a test, it comes with the paperwork you need to go to your local pathology centre for a blood test. Your sample is analysed in ImuPro’s German laboratories where we may detect the presence of IgG antibodies related to up to 270 foods. We then divide these foods into three groups: not elevated, elevated and highly elevated.

These results offer you a basis for dietary changes to ease your symptoms. Often that involves eliminating certain foods to help reset your gut, then reintroducing them one at a time and monitoring your symptoms.

Order your test today.


*All information is general and is not intended to be a substitute for professional medical advice. 


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