I suffer allergic rhinitis - chronic hayfever, basically. It's a nuisance in spring and summer, but medication can control it.
My ex-boyfriend said that he's allergic to strawberries, and I told him that eating more strawberries and drinking more strawberry milkshakes will cure him, but he didn't listen to me.
Allergies do not work like that. It's a very common misconception, one that's extremely dangerous to people who actually suffer allergies. A true allergy - rather than a mere sensitivity - means a person is genetically incapable of coping with the allergen in question. I have a friend who very nearly died when a relative secretly gave her "just a little bit" of a plant chemical that she's allergic to.