Why Is One Allergic To Fruits And Nuts?

I have been allergic to fruits and nuts for over 20 years now. I am tired of not being able to eat them, with how beneficial they are and how yummy they are. I get what has been called herpes of the mouth and have gone into anifilactic shock after eating an entire bowl of strawberries. I get sores in my mouth that hurt and my throat closes up if I eat too much. What can I take so I CAN eat these things?