Food allergies: Symptoms, causes, testing and treatment

Deadly reactions
The deadly reaction Susan suffers is anaphylaxis – an extreme response that involves multiple organs and systems in the body, including the skin, lungs, heart and respiratory system. Reactions often start with itchiness and swelling in the mouth, on the skin and in the throat, and rapidly progress to trouble breathing. Blood vessels expand, leading to a deadly drop in blood pressure, which causes the heart to stop. Anaphylaxis is triggered when the IgE antibody recognizes something it has identified to attack, and the immune system goes into overdrive to deal with it. The nonprofit support group Anaphylaxis Canada notes that up to two per cent of Canadians live with the risk of anaphylaxis – some from wasp or bee stings, others from specific foods.

Julie Kartzewski from Burnaby, B.C., is more than familiar with anaphylaxis. She's been hospitalized with it nearly a dozen times due to a nut allergy. When she eats a food she's allergic to (always unintentionally), she feels itchy all over, her mouth and throat swell, her eyes and lips get puffy and hives break out over her face. "Then I get a tightening in my chest and it becomes difficult to breathe," she says. As soon as the early signs of trouble occur, she injects herself with a device she carries around – an epinephrine auto injector – then immediately heads to the nearest emergency room. Two products, EpiPen and Twinject, contain epinephrine, a drug that gives the heart a temporary boost (for about 30 minutes) – just long enough for most people to get to a hospital.

A surprisingly difficult aspect of having a food allergy is avoiding the food, since it's often a "hidden" ingredient. Julie had her last anaphylactic reaction when she bit into an éclair in which the whipped-cream filling had been mixed with almond paste. Another time she ate pesto that had walnuts as an ingredient.

"You get used to reading food labels," she says. But even then you have to be careful; an ingredient can be listed under different names. For instance, whey is a milk product and can wreak havoc in people with a milk allergy.

How to avoid attacks
Avoiding foods you're allergic to, reading labels and carrying an epinephrine auto injector are key strategies for people living with food allergies, says Dr. Peter Vadas, an allergist, immunologist and associate professor of medicine at the University of Toronto and director of the division of allergy and clinical immunology at St. Michael's Hospital.

At restaurants, it's important to ask staff about food ingredients and how something is prepared. You need to be wary of imported foods, too, since food-labelling laws vary among countries, and accuracy can't be guaranteed. For instance, Vadas says, labels on chocolate bars from Europe often don't say they may contain peanuts.

Because of her extreme allergy, Susan, who loves eating out, often avoids it. She hates living with an extreme allergy and says that asking servers in restaurants detailed questions about ingredients or how food is prepared makes her feel like a fussy customer. Then again, even the tiniest exposure could be a death sentence.

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