Nutrition – Allergy or intolerance?

Am I intolerant, or is it an allergy? I often hear these terms used interchangeably when it comes to the reactions that people may experience when eating certain foods. However, there is an important difference between them. The most important difference is that one can be life-threatening, whereas the other just makes life uncomfortable.

A food allergy is caused by an exaggerated immune response to a food. When you eat the particular food, your body responds as if it is a pathogen that needs destroying. Our bodies destroy pathogens by producing antibodies, and with an allergy we produce an excessive amount of immunoglobulin E (IgE), which can cause a range of symptoms including hives, itching, swelling, vomiting, diarrhoea and nausea; and in some cases anaphylaxis, which is life-threatening.

An allergy reaction occurs very quickly – within seconds or minutes, and often dramatically. Allergies can be tested for, either by a skin prick or a blood test. If IgE antibodies are found, in response to coming into contact with a food, or any other compound, then we can be pretty confident that you are allergic to that food/compound.

In contrast, a food intolerance doesn’t involve your immune system. There are no antibodies produced, and reactions can occur within a few minutes or after several hours. Thankfully, the symptoms are not life-threatening, but they can be unpleasant and painful. The most common symptoms are usually gut-related, such as bloating, flatulence, diarrhoea, indigestion and nausea, although sometimes an intolerance may aggravate eczema or asthma.

Unfortunately, diagnosing food intolerances is not as easy as diagnosing a food allergy. There is no easy blood test and the symptoms are often the same as other health conditions. The standard method to diagnose food intolerances is through a detailed food diary and symptom diary, and elimination-reintroduction food challenges. These are difficult to do alone, so it’s best to find a dietitian or registered nutritionist to help navigate this.

You can find food intolerances tests online. They usually test for an antibody called immunoglobulin G (IgG). IgG antibodies are found in our blood because you have eaten a particular food, not because you have an intolerance, although an IgG test can inadvertently identify a food intolerance. For example, the test says you are intolerant to 15 foods, so you cut them all out and ‘hey presto’ the food intolerance symptoms you were struggling with go away. The problem is that you don’t know which of those 15 foods was causing the symptoms, so now you’re eating a restrictive diet that’s impacting on your nutrient intake as well as your social life.

If you suspect that you have a food allergy or intolerance, your first stop should be your GP to work out which it is, and to rule out any other health conditions. Then, find a dietitian or registered nutritionist who can help you to work around the allergy or manage the intolerance, so that you can continue to have a well-balanced and diverse diet.