ABSTRACT
I. INTRODUCTION IgE-mediated allergy affects more than 25% of the population (l). Besides mites and grass pollen, trees are the most important allergen sources (2). Pollen, fruits, and seeds are the major allergen-containing elements in trees. Wind-pollinated trees with heavy pollen production are the major sources of respiratory allergens. Other trees bear fruits and seeds that may cause different forms of food allergy. In the northern and middle parts of Europe and North America and in certain parts of Australia, birch (Betula verrucosa), belonging to the order Fagales, represents the most important elicitor of respiratory manifestations of allergy (e.g., rhinitis, conjunctivitis, and asthma) (3). Other trees belonging to the same botanical order (hazel, alder, hornbeam, oak, and chestnut) contain cross-reactive allergens and also represent major triggers of allergic symptoms (4). Botanically distinct tree species
(e.g., Rosaceae) may contain allergens in their seeds (fruits), which cross-react with pollen allergens and therefore elicit food allergy in pollen-allergic individuals (5,6).
