Items of Interest
Allergy Cross-Reactions: When Birch Meets Apple
As friends herald the melting of the snow with the glee of a lottery winner, it’s often hard for the tree allergic to join the celebrating. They know that their foes – birch, elm, maple, alder, poplar and their nasty ilk – have begun to churn out clouds of tiny allergy-causing particles. It won’t be long before the runny nose, the wheezing or the red itchy eyes predictably begin again.
Not only do a third of us battle hay fever, but for a significant proportion of these allergy sufferers, the spring bloom is just the start of their allergy woes. Dr. Antony Ham Pong, an Ottawa allergist and clinical researcher, estimates that up to 10 per cent of the general population has a condition called oral allergy syndrome, or OAS. It’s a less severe form of food allergy, directly related to pollen reactions, that’s known to set off tingling and unpleasant itching in the mouth, throat and lips. Reactions are caused by a variety of fruits, vegetables, nuts, seeds, and even spices; all of which share allergenic proteins with specific hay fever-causing trees and plants.
“Nobody talks about the foods causing oral allergy syndrome because it’s not considered a life-threatening allergy,” says Ham Pong, the author of several articles educating patients and doctors about OAS. “But it’s actually more common than peanut, milk, egg, and fish allergy.”
In springtime, the big cross-reaction offenders are the birch and alder trees. Depending on where you live, anywhere from 20 to 70 per cent of people who are allergic to birch and alder pollens will also have OAS. Ham Pong estimates about a third of birch-allergic Canadians are affected, but the incidence of OAS is even higher in some European countries. Although OAS is relatively common, he doesn’t think it is increasing, at least not in North America. Rather, doctors have become better at spotting this condition.