One in every 13 Canadian suffers from a significant food allergy, according to the first-ever nationwide study.
The research, published in the Journal of Allergy and Clinical Immunology, found that about 7.5 per cent of children and adults have at least one food allergy.
"It's a significant number," said Ann Clarke, an allergist at the McGill University Health Centre in Montreal and co-author of the study.
She said it is not clear whether the number of people with allergies is on the rise or there is just more awareness, but research like this will help establish a base for comparison in the future.
Dr. Clarke said what is more important than the number is the fact that "many people with food allergy are not properly diagnosed and experience repeated exposure that places them at risk of anaphylaxis." (Anaphylaxis is a potentially life-threatening allergic reaction.)
That is why AllerGen NCE Inc., a network of researchers, is trying to establish a national anaphylaxis registry to track cases and ensure Canadians with severe allergies get proper treatment and follow-up.
Dr. Clarke said that systematically tracking reactions can, for example, help identify foods containing undeclared allergens and expedite recalls.
"This registry will fill a crucial role; it will, hopefully, lead to the prevention of avoidable deaths," she said.
The new findings are based on a survey of 3,613 Canadians who were asked a series of detailed questions about allergic reactions and symptoms.
Dr. Clarke said while the method is not perfect, she was pleased to see that the numbers were comparable to smaller studies in which people underwent allergy testing.
According to the research, about 2.5 million Canadians suffer from food allergies, or about 7.5 per cent of the population.
• 1.93 per cent with peanut allergy;
• 2.36 per cent with tree nut allergy;
• 0.99 per cent with fish allergy
• 3.02 per cent with shellfish allergy; and
• 0.19 per cent with sesame allergy.
(The total exceeds 7.5 per cent because some people reported more than one serious food allergy.)
Researchers found that peanut and nut allergies were much more common in children than adults and the opposite was true with fish and shellfish allergy.
A second related study that examined Canadians' perceptions about allergies found that the problem is perceived to be much more common than it is in reality.
"Ask how many are affected by [food]allergies and the response is 30 per cent on average," said Susan Elliott, the dean of applied health sciences at the University of Waterloo. "That's a huge mismatch with the 7.5 per cent."
What that means, in a nutshell, is that "people are worried," Dr. Elliott said.
She noted that the only practical protection available to those with food allergies is avoidance of allergens so they are very dependent on food labels.
But the survey revealed that "people are really confused. There are too many types of labels and it's not always clear what they mean."
Samuel Godefroy, director-general of the food directorate in the health products and food branch of Health Canada, said that message has been received loud and clear.
"We're going to improve labelling rules as a result of this research," he said. New regulations on food labelling will be published by the end of this year, Dr. Godefroy said.