If you were to ask people on the street what are the most common food allergies, they would likely answer: peanuts, nuts, seafood, wheat or milk.
But sesame? Probably not. So how did it land on Health Canada’s list of priority allergens?
In short, in the ‘80s and ‘90s sesame became more common in breads, the popularity of traditionally Middle Eastern foods such as hummus skyrocketed, and bagels, which are often coated with sesame seeds, became a mainstay in the mainstream North American diet.
At the same time, allergists began seeing more and more patients who had experienced serious reactions to the tiny seed – in some practices it even became more common than shellfish and fish allergies – and they suspected that its increased use in our diets was to blame.
Sesame allergy is also seen more commonly in kids who have peanut allergies, and peanut allergies are on the rise, so researchers believe that might be pushing the sesame allergy rates even higher. See: Sesame Seed Allergy Prevalence 
But because sesame allergy has only recently come to the fore, some regulatory bodies have yet to catch up. In the United States, food manufacturers must clearly declare the top allergens on its product labels – but as yet, sesame has not yet made that list, so it can still be hidden as “tahini”, “spices” or “natural flavoring”. (It’s also used in cosmetics and pharmaceuticals.)
In Canada, sesame was added to the priority allergens list in 2000, and so must be named on product labels; it is also a priority allergen in Europe.