Pollen-food-allergy syndrome is also (more commonly) called
Oral Allergy Syndrome.
Basically, the immune system 'sees' some food proteins as being pollen proteins instead.
The most common OAS connections/cross-reactivity are:
birch pollen --- apple, pear, peach, plum, cherries, etc.
ragweed-- melons, bananas, and a few other random things
grass-- hazelnut (and more rarely, peanut)
In
most people-- such reactions are oral only, and merely uncomfortable or annoying. Generally comprised of itching, maybe even other odd sensations in the mouth and throat. They may only occur when the pollen is in season, or in those more severely effected, all year long. With the nut-grass cross reactivity, though-- it is SUPER important to have a really top notch food allergy specialist help you tease it apart, because nut allergy is SO dangerous for so many people.
Cooking raw fruits/veggies that trigger the response
mostly eliminates the reaction because of how heat-sensitive the culprit proteins are.
HOWEVER... any oral symptoms that result in swelling
are more serious, regardless of the cause. It's also true that some people have a predisposition to systemic allergic reactions, and in those individuals (and there's no great way to know who they are until you have reaction history that says you're one of them) OAS
is dangerous.
Glad that your DD has epipens and isn't afraid to use them.