TORONTO – Medical researchers have a clearer picture of the prevalence of food allergies in Canada after a survey found more than three per cent of individuals were allergic to at least one of five foods.
The survey of 9,667 individuals has yielded the first nationwide data on allergies to peanuts, tree nuts, fish, shellfish and sesame, researchers said. They found that 3.2 per cent of people had a probable allergy to at least one of the five items.
The findings were distributed Monday by AllerGen, a national network of researchers focusing on allergies and related immune diseases. Results were also published recently in the Journal of Allergy and Clinical Immunology.
“It’s important to know how much of a problem this is in Canada,” said co-author Dr. Ann Clarke, a professor in the department of medicine at McGill University in Montreal.
“It’s important to have some sort of baseline so that this can be followed over time.”
She said there have been American surveys, and numbers from the United Kingdom indicate prevalence has increased since the 1990s, at least for peanut allergies, but there weren’t really any nationwide numbers in Canada.
“This is the first such data, and it’ll be very interesting to see what these numbers are like five, 10 years from now. Are these numbers increasing? Are they decreasing, are they remaining stable?”
Laurie Harada, executive director of Anaphylaxis Canada, said food allergies are a growing public health issue.
“I think some of the data’s going to help influence things like policy decisions in terms of food labelling, the way that manufacturers are catering to a public that has a growing health concern,” she said in an interview.
“It impacts our school system as well.”
Individuals were said to have a probable allergy after a series of detailed questions found they had “an appropriate history suggestive of a food allergy or confirming a food allergy.”
The prevalence was 0.93 per cent for probable peanut allergy – 1.7 per cent among children and 0.7 per cent in adults.
“There can be several reasons for why it’s much higher … in children, but certainly one of the reasons would be that people can outgrow peanut allergy, about 20 per cent, and another possible reason is that peanut allergy may be increasing with time,” Clarke explained.
The peanut allergy numbers are in line with estimates from a previous study of children in Montreal, as well as American estimates.
The prevalence of probable allergy to tree nuts overall was 1.14 per cent, and again, it was more common in children. But the reverse was true for fish and shellfish.
“Overall, the prevalence was for fish, 0.5 per cent, shellfish 1.4 per cent, but here we see the opposite picture as we do for peanut and tree nut, with these allergies being more common in adults.”
Sesame allergies weren’t very common, and had an overall prevalence of 0.1 per cent.
A portion of the telephone questionnaire dealt with whether a person with a probable food allergy had seen a doctor about it.
“When we look at children, about 90 per cent had gone to a doctor for peanut testing, for example,” Clarke said.
“When we look at adults, for example, you see only about 70 per cent of the adults going to a doctor for testing. Certainly when you look at shellfish, which is really more of an adult allergy, you see only about 50 per cent of adults went to a doctor for testing.”
Clarke said confirmation by a physician is important.
“Right now the only management for allergy is to avoid eating the food completely, and if you do have a reaction to treat yourself with … an EpiPen or a Twinject, which is basically you inject yourself with adrenaline, which is a life-saving medication for severe allergic reaction.”
“So clearly it’s critical to know if you or your child are allergic so that the food can be avoided, and if ingested accidentally the appropriate treatment can be given.”
About 50 per cent of individuals who reported an allergic reaction carry an epinephrine auto-injector “so certainly a lot of people are not carrying it,” Clarke said.
It’s also important to know if you’re not allergic to a food so that you don’t need to avoid it or carry around the adrenaline, she said.
“There’s a lot of knowledge gaps in the diagnosis and the management of food allergy,” Clarke said.
Harada, whose 16-year-old son is allergic to peanuts, tree nuts, shellfish, chickpeas, split peas and soy, emphasized the importance of food-allergic individuals carrying an EpiPen or Twinject, and knowing how to use it.
“Those are must-have medical devices that people must carry with them at all times because you never know when you’re going to have an accident. Because accidents do happen, despite best efforts.”
