KarenDarden, that advice wont do a thing to stop a reaction to fruit. I strongly advise the person who asked the question does not follow your advice, esp as her reactions impede her breathing.

I suspect that the cause lies with tree pollen allergy, reactions to fruit and veg are linked to oral allergy syndrome.
tomato has lots of histamine that does get cooked off when heated to high temp. however other proteins within fruit and veg have a link to the protein in pollen,
some people will be able to eat for example apple in winter months because their system is not reacting to tree pollen, but find they cant eat it in spring or summer.
some will react to certain fruit and veg all year round , because their body has been highly triggered by tree pollen allergies.

my son can now only eat bananas and the odd grape as most fruit causing reactions, he has and will never be able to eat tomatos, and current nasty reactions to apple ( the most common one that causing OAS) and strawberries, mango and pineapple. and marmite/bovril due to yeast extract being high in histamine.

this is part of a pattern of being allergic to all environmental allergies, his tree pollen being the worst.

his sister now has similar fruit issues, grapefruit, strawberry and mango due to the increasing severity of her pollen and hay fever symptoms.

Sounds like what I have Salicytate Intolerance. It is in the skin of most fruits and veggies. It is a natural enzyme to protect plants against bugs. Tomato, avo are some of the no goes! If you need more info contact me. It is also found in cosmetics and medicine! Best advice is to run blood tests to determine if you can Salicytate intolerence. I can only eat bananas that safe!! Contact me if you need more info xx

Histamine also in fruits and veggies

i have a lot of enviromental allergies - so pollens, trees and grasses. and there are quite a few fruits/veggies that can become infulenced by their environment and carry those pollens into the fruit while its growing. so then you eat the fruit and you get a reaction. ive had reactions to watermelons, cucumbers and tomatos. so thats somehing else to consider.

Prepare a water vinegar solution to soak fruits and vegetables about 15 minutes. Wipe dry and store. If you have no reaction the preservatives sprayed on the fruit and vegetables is the problem!