Saturday 18 November 2017

Food allergies: the great myth

There is all manner of misinformation about food allergies online. Consultant immunologist Dr Mary Keogan separates fact from fiction with our reporter

If you think you have a food allergy, your first port of call should be your GP
If you think you have a food allergy, your first port of call should be your GP
Katie Byrne

Katie Byrne

Gluten-free, wheat-free, dairy-free… The teeming 'free-from' sections in most supermarkets - coupled with the dietary advice dispensed on today's health and wellness blogs - may suggest that we all have a food allergy of some description.

And yet, despite the booming industry of gluten-free foods and at-home allergy tests, medical professionals insist we haven't suddenly become insensitive to certain food groups.

Dr Mary Keogan is one of them. The consultant immunologist at Beaumont Hospital hasn't observed a rise in food allergies or intolerances per se. On the contrary, she has noticed a rise in misinformed patients who self-diagnose in the office of Dr Google or opt for what she calls 'back-of-the-supermarket' allergy tests.

According to Dr Keogan, the most dangerous myth is the idea that non-validated allergy tests have clinical integrity.

"There are numerous guidelines from allergy associations the world over that would all agree that allergy testing begins with a careful history," she explains. Unfortunately, most at-home, non-clinical and unconventional allergy tests neglect to conduct what should be a routine background check.

"What is offered - with varying levels of sloppiness - is, first of all, testing for IgG antibodies," explains Dr Keogan. "Yet the presence of IgG does not indicate an allergy. Many of us have IgG antibodies to foods that cause us absolutely no problem."

Dr Keogan is equally critical of hair analysis allergy testing - "It's used in toxicology but absolutely useless in terms of allergy testing" - as well as VEGA testing, which measures electrical impulses from the body when it is in contact with certain food groups. "It's not biologically plausible," she says.

These tests often result in the patient eliminating a food group from their diet. However, this can cause more harm than good when it is not done under medical supervision.

"What a lot of people don't realise is that if they have put themselves on a gluten-free diet then the blood test for coeliac disease can become negative, even if you have a biopsy taken.

"Coeliac disease is an immunological reaction to gluten. The treatment is that you take away gluten completely and then the lining of your gut returns to normal.

"So if you have a biopsy done after you have put yourself on a gluten-free diet, the biopsy can look normal." she explains.

"Unfortunately, if you are sensitised to a food but tolerant, and you then cut it out, there is a risk that you can become clinically allergic to the food. Remember, part of what's maintaining your tolerance is that you're exposing your immune system to the food on a regular basis."

Patients also run the risk of introducing foods they may not be able to tolerate.

"By taking gluten out you have to put something else in. And that something else can cause problems. We're beginning to encounter patients with allergies to things like buckwheat, which is commonly used in gluten-free products. The reason they react is because it's new to their immune system."

According to Dr Keogan, patients can often misattribute symptoms to specific allergies. "The idea that bloating is always related to food allergies is incorrect," she says. "The most common cause of bloating is the muscle in your gut is acting in a disorganised way.

She has also encountered patients who believe that they may be allergic to a component in certain alcoholic beverages. In rare cases, they may be diagnosed with chronic spontaneous urticaria and angioedema, an autoimmune condition that is exacerbated by alcohol and causes hive-like swelling. However, in most cases, the symptoms they describe are no more than "a really bad hangover".

She recalls a patient in her early 20s who was drinking 16-20 units a night, a few nights a week. "What she kept saying to me was 'But my friends can do it'."

"I've been doing immunology since 1989 and I have seen just one person who was genuinely having an allergic reaction to mushrooms and yeast [which is present in wine and beer]."

Wheat intolerances are also uncommon, while lactose intolerance is "vanishingly rare" in Caucasians. "It is extremely common in other parts of the world, though," she adds.

Dr Keogan also points out that it is "very unusual for an adult to develop an allergy to a food that they have been eating all along".

Even so, many people report weight loss and renewed energy after using a non-validated allergy test. Surely the practitioners are getting something right? Dr Keogan disagrees. "If you put anyone on an exclusion diet, it drives down calorie content and they lose weight."

Her advice may be difficult for some people to digest, but it's echoed by the medical community at large. If you think you have a food allergy or intolerance, your first port of call should be a GP.

* Dr Mary Keogan will be speaking on this topic at a free patient information evening at Beaumont Hospital on Wednesday, May 18 from 6.30pm-7pm. Register for the event at or call 01 809 2022

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