Food and nutrients can protect against the development of allergy. Bioflavonoids, a class of antioxidants found in vegetables, fruits, teas, herbs and spices, inhibit excessive activity of the enzyme NOX, which contributes to respiratory tract damage in people with asthma and rhinitis. High dietary consumption of bioflavonoids decreases the incidence of allergies and asthma.
In one study, Australian scientists had adults with asthma follow two diets and change nothing else. The high-antioxidant diet contained five servings of vegetables and two servings of fruit a day, and the low-antioxidant diet contained no more than two servings of vegetables and one serving of fruit a day. After two weeks, people consuming the high-antioxidant diet showed better lung function on breathing tests than did the people on the low-antioxidant diet.
Other nutrients that prevent the development of allergies are:
Low levels contribute to allergy in general, the development of allergic rhinitis and the occurrence and severity of asthma. Sunlight and oily fish are good sources.
A mineral that is often low in people with asthma and eczema. Pumpkin seeds, egg yolk, clams, oysters, beef and dark-meat poultry are the richest sources.
An antioxidant mineral that is often low in people with asthma. Although most Americans get their selenium from grains, Brazil nuts and seafood are the most reliable sources.
Low consumption is associated with increased risk of asthma and total allergic sensitization. Top dietary sources include buckwheat, kidney beans, navy beans, soybeans, green beans, spinach, black-eyed peas, Swiss chard, broccoli, kale, almonds, cashews and hazelnuts
Vitamin E (as alpha-tocopherol)
Reduced vitamin E intake is associated with allergic sensitization and asthma. Nuts and seeds are the best dietary sources.
Higher intake is associated with decreased risk of asthma in children, and reduced intake from food or lower levels in the blood are each associated with asthma in adults.
Higher omega-3 intake from fish is associated with reduced incidence of asthma in young adults.
Foods as Triggers for Seasonal Allergy
In contrast to the protective effect of nutrients, certain foods may increase symptoms of seasonal allergy by cross-reacting with airborne allergens. Cross-reactivity occurs when the protein in a food is similar to the protein found in a specific pollen and aggravates symptoms during the allergy season. This effect has been most strongly documented for birch pollen.
Researchers in northern Europe, where birch trees abound, have found that almost three-quarters of people with birch pollen allergy are allergic to plants that contain proteins similar to the main birch pollen allergens, which are called “Bet v 1” and “Bet v 6.” At Germany’s Paul Ehrlich Institute, about 70 percent of patients allergic to birch pollen experience symptoms when exposed to birch pollen foods, which include apples, celery, carrots, hazelnuts, soybeans, peaches and other stone fruits, oranges, lychee fruit, strawberries, persimmons and zucchini.
Ragweed and grass pollen, in contrast, contain proteins called pan-allergens that cross-react with pan-allergens in food. Pan-allergens are the allergic triggers for about a third of all pollen allergies and are the likely triggers if a person with pollen allergy is also allergic to melon, watermelon, bananas, citrus fruits, tomatoes or latex.
Pan-allergens may also provoke symptoms outside the respiratory tract, including hives, diarrhea, abdominal cramps, anaphylaxis and itching or swelling of the throat or lips. This is called the oral allergy syndrome. Sometimes pan-allergens require an additional factor like exercise or the use of pain killers (aspirin, ibuprofen or naproxen) to provoke symptoms.
Although pollen-related food allergens are often destroyed by cooking, recent studies have shown that hazelnuts and celery may provoke symptoms even after being thoroughly cooked.
Yeast and Mold in Foods
People allergic to inhaled molds commonly show allergic reactions to oral challenge with mold or yeast extracts. Common dietary sources include bread, crackers, beer, wine, other fermented beverages, vinegar, pickled vegetables, dried fruit, aged cheese, many commercial sauces and mushrooms. Consuming these may aggravate symptoms associated with environmental mold allergy.