A healthy, balanced diet that follows the recommendations of the Food Guide Pyramid is the first key to defending your body against allergic reactions. A healthy body is more resistant to attack, whereas stress, poor diet, insufficient sleep, emotional trauma, and infection can predispose your body to allergic reactions. More specifically, vitamin C and vitamin E can help protect your body. Vitamin C will boost your immune system and is found in citrus foods such as oranges, grapefruit, orange juice, grapefruit juice, green peppers and many beverages. Vitamin C acts similar to an antihistamine.
Vitamin E is found in plant oils and green, leafy vegetables.
With allergies in mind, the best diet to follow is one with plenty of carbohydrates and fresh fruits and vegetables. Thirteen years ago I became allergic to cantaloupe. By sick, I mean vomiting, diarrhea and cold sweats. About seven years ago bananas did the same thing, three years ago it was watermelon. Now there are three fruits I have always eaten that I am afraid to eat.