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.