Oral Allergy Syndrome (OAS)

Suppose you eat beef at lunch with no reaction and drink milk at dinner with no reaction, but when you eat both at the same meal, you break out in hives. This is called a cross-reaction, be­cause you're responding to the cumulative effects of two mem­bers of the same food family.

Cross-reactions occur with nonfood substances, too. For in­stance, you may be able to eat cantaloupe most of the year, but when certain grasses begin to pollinate, you find that you can't tolerate the melon. This type of allergic reaction, the cross-reacting of identical allergens present in pollens and fresh foods, is called oral allergy syndrome, or OAS. The symptoms are itch­ing and swelling of the lips, tongue, mouth, or throat.

Take another example: You're eating a peach in the kitchen with the windows closed. You decide to sit in the garden, but as soon as you venture outside, the combination of peach and pol­lens makes your lips swell.

You'd be right to suspect anaphylaxis because it could be the start of a severe reaction, but if your symptoms stop at the mouth and throat and don't affect your skin, temperature, or breathing, you're probably safe and the swelling should disappear by itself. Be aware that with all food allergies, however, the worst that can happen can happen—and you could end up in the emergency room being treated for anaphylaxis.

If there's the least suspicion that you might be having an anaphylactic reaction, don't wait to find out. Reach for the epinephrine.