Allergy or intolerance: What's the difference?

Friday 9th February 2018 - Health & Living , Irish Independent View Article Here

There's an increasing trend towards using the terms 'intolerant' and 'allergic' as interchangeable - but the reality is that the two are very different things.

A food allergy is an immune reaction to food proteins. Essentially a food protein, the allergen, causes the body's immune system to react, which can effect different organs in the body, producing a variety of symptoms. At it's most severe, an allergy can be life-threatening.

An intolerance is not a life or death affair. The immune system is not involved, symptoms are generally less severe and usually limited to digestive issues such as bloating, wind, loose stools but also sometimes rashes, joint pain and headaches. A food intolerance can adversely affect your long-term health, but it will not cause anaphylaxis.

The common culprits of an allergy and an intolerance also differ slightly. Of the most common food allergies (see page 10), the 'big three' are cow's milk, eggs and peanuts. According to, the foods most frequently associated with an intolerance in Ireland are milk (lactose intolerance), gluten (coeliac disease, wheat intolerance) and certain food additives like monosodium glutamate (MSG).

Other frequent offenders include red wine, cheese, caffeine and salicylates (chemicals found in certain vegetables, herbs, spices, fruits and chocolate).

Allergic reactions often, but not always, reveal themselves early in life while food intolerances commonly are more associated with adults than children.

In any case of a food hypersensitivity, be it an allergy, aversion or intolerance, it's important to seek medical diagnosis from a qualified professional. In both cases, a health care professional will do a physical examination, take a detailed history of your diet, symptoms and suspected triggers.

An allergy expert will take a skin prick test and/or a blood test - which they alone have the skills to interpret.

There is no solid scientific support for tests used to diagnose food intolerances. Just last month, the PSI (the pharmacy regulator) and the HPRA (Health Products Regulatory Authority) announced that pharmacists should not offer food intolerance tests.

"The only clinically valid method for the diagnosis and treatment of food intolerance is an elimination diet, which should be carried out under the supervision of a registered dietician or medical professional," says Niall Byrne, Registrar of the PSI. "With regard to all products promoted as tests for food intolerance, the HPRA has determined that there is no single test available to diagnose food intolerance."

A wealth of allergy tests also exist, but Professor Jonathan Hourihane, one of Ireland's two qualified allergy specialists, stresses the importance of leaving diagnosis of an allergy in the hands of the professionals.

"You can take one of these blood test and get a positive signal from a food allergy but it's 50/50 whether that's true or not," he explains. "Irish people are getting tested for these things and we get people referred to us on the basis of these tests. It's frustrating. We spend far more time telling people that they're not allergic to something than finding out that they are, or revealing something to them that they didn't know they were allergic to."

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