Oral Allergy Syndrome is an allergic response to certain types of fruits, vegetables and/or nuts that may occur in people who have an existing allergy to tree, weed or grass pollen.
|The itchy, watery eyes, or that sudden tingling, itching or burning sensation in your mouth is all too familiar: it must be ragweed season again.|
You walk outside, and the summer air is anything but fresh but you endure the symptoms which thankfully start to wane. Later that night, after your soccer game, the juicy watermelon you share with a friend makes your tongue and lips swell. Your stomach is hurting the whole car ride home, and you decide that maybe next time you will have to pass on the watermelon.
But this is strange: you knew you were allergic to ragweed, but your reaction to watermelon is brand new.
Although there is still so much we do not know about allergies, we do know that certain types of foods, or pollen like ragweed, are common culprits when it comes to giving the body an allergic reaction. Put in the simplest terms, allergic reactions happen when a person’s immune system recognizes certain proteins called allergens, as foreign or unsafe. The body’s immune system then triggers an allergic response, like the swelling in your tongue and lips, to fight off the allergen.
Reacting as if allergic
However, some allergies can be much more complex, even downright sneaky.
Oral Allergy Syndrome (OAS) is one such allergy. Certain types of fruits, vegetables, and nuts can trigger OAS but the strange part is you can also develop OAS even if you are not allergic to any of these foods. With OAS, even if you are not allergic to watermelon, you can still have an allergic response when you eat it. A pollen allergy, for example to ragweed, can be activated after eating certain fruits, vegetables, or nuts.
You can react to something you are not actually allergic to because your immune system gets confused. Many of the proteins that cause allergic reactions are very small and similar in structure. The protein molecules that make up the watermelon were mistaken by your immune system for harmful pollen allergens. Your immune system triggers the allergic response to fight off the protein molecules because it thinks they are harmful pollen allergens, like those found in ragweed. Basically, your ragweed allergy and a confused immune system are the reasons you reacted to the watermelon.
If you have an allergy to birch, you can react to apples, carrots, or even almonds. An allergy to mugwort, another type of weed, can give you a reaction to watermelon. These are just a few examples of the fruits, vegetables, and or nuts that can be involved in OAS, a tricky allergy that can make you wonder why removing yourself from a known allergen doesn’t always solve the problem. If you think you might have OAS, speak to your allergist.
This article was written by the registered dietitians at the Specialty Food Shop at Toronto’s SickKids Hospital.
Thank you to AboutKidsHealth.com