But the patients coming through Ham Pong’s offices in Ottawa and Vancouver were telling a very different story. Not only were more of them reacting to sesame, but those reactions tended to be severe; in fact, more of his patients were experiencing full-blown anaphylaxis from eating sesame products than from shellfish.

A more formal survey of more than 2,000 patients confirmed the allergist’s suspicions – but many of his colleagues were still not convinced. “I presented a study at an allergy meeting, and one of the allergists didn’t believe that sesame was a problem. So he asked parents for a show of hands of how many of their children had sesame allergy, and he was very surprised “at how many hands went up,” recounts Ham Pong. “It took him aback because there was no published literature on its prevalence at the time.”

Since then, there has been a significant amount of scientific literature to show that sesame is yet another one of those especially problematic foods, to the point where the European Union and Canada have added it to their priority allergen lists, which include peanuts, tree nuts, dairy, wheat, eggs, fish, shellfish and soy. The United States is investigating whether to follow suit.

But sesame isn’t the only new culprit to gain priority status in Canada; nor is it the only emerging allergen on the radar of North American scientists. The fact is, our diets are constantly in flux – often because particular foods are found to have special disease-fighting properties and become trendy, or because people from around the world bring their culinary influences with them when they arrive on North American shores.

In turn, those foods – from sushi to hummus to curry – get woven into our ever more colorful mainstream diet. Those constantly changing grocery lists, however, mean that our society’s allergies are bound to see shift as well.

“Until kiwi became popular because of the high levels of vitamin C, you didn’t see a lot of kiwi allergy – but now you see a fair amount because it’s a very allergenic fruit,” says Ham Pong. “But if there wasn’t much of it in the diet, it wouldn’t really be an issue. So what makes a food a problem in society is how allergenic the food is, and how much that food is adopted as part of the daily diet.”

Open Sesame

That’s likely what happened with sesame, says Dr. Robert Wood, director of pediatric allergy and immunology at the Johns Hopkins University School of Medicine in Baltimore. The seed became more common in breads, the popularity of traditional 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.

And unlike some oils such as peanut and corn whose proteins are almost entirely removed during the refining process, Wood adds that sesame is a raw oil, and as a result can be just as allergenic as the seeds themselves.

“In our practice, it has become much more common, and appears to be the fourth or fifth most common allergen we deal with,” says Wood. In addition to pointing the finger at the increased prevalence of sesame in our diets, Wood says that one of the most notorious allergens on the list may also be adding to the problem.

“We see sesame allergy more commonly in children who also have a peanut allergy, and we suspect that there are some similarities in the allergens in sesame and peanuts,” he explains. “So there may be some of the sesame allergy that’s actually being driven by the increase in peanut allergy.”

But because the prevalence of sesame allergy is relatively new, 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 flavouring”. (It’s also used in cosmetics and pharmaceuticals.)

In Canada, sesame was added to the priority allergens list in 2000, and mustard is in the process of being added as well, but the country has yet to enact new regulations that require manufacturers to label all priority allergens in clear language.

You’re sitting there eating and all of a sudden, your lips (or tongue and palate) begin to swell.

There might tingle or itch at the back of your throat, or you might start to sneeze, have the urge to blow your nose or rub your eyes because of tearing.

While that is usually the end of it, symptoms do cover the spectrum, from what looks like a fat lip all the way to vomiting, diarrhea and, on rare occasions, anaphylactic shock.

Who’s at Risk?

Those who have allergies to pollen from trees (such as birch and alder), and/or  ragweed and grass pollen.

In Europe and Asia, those allergic to mugwort pollen, also commonly get symptoms to certain fruits, vegetables, spices and seeds.

See Also: Chart on Cross Reactors

Roughly one-third of North Americans with pollen-related allergies are thought to be affected. It’s not clear why the other two-thirds of hay fever sufferers are not similarly affected.

Managing the Condition

Unlike pollen-related hay fever, OAS does not go away because the offending allergens – stress-related proteins that begin to build up as soon as the food is harvested – continue to multiply.

To avoid or mitigate its effects, doctors recommend you manage your hay fever symptoms through antihistamines, an intranasal steroid or seasonal allergy shots.

Do Not: Eat any of the fruits or vegetables on your list of offenders in their raw form. Bake them, broil them or even microwave them for one minute at between 80 to 90 degrees Celsius. Make a pie or make preserves.

Do: Try peeling fruit because scientists say the allergens tend to concentrate in the skin. Others slice fruit and leave it exposed for half an hour before eating it.

Do Not: avoid all foods on the lists, only the ones you have reactions to.

Be aware: You may increase the severity of an OAS reaction by drinking alcohol or exercising after consuming an allergenic food.

More serious cases
In more severe OAS cases, a regimen of year-round allergy shots can help, allergists suggest carrying an epinephrine auto-injector (the brands are EpiPen or Twinject). Consult your doctor for more information on your own case.