Λεξικό .. Birch, common silver [(L) Betula verrucosa or B. pendula]

Silver birch is a single-stemmed deciduous tree up to about 25 meters. Birch is found in woods on lighter soils and healthland and often cultivated. Silver birch is native and common in most Europe, northwestern Africa and western Siberia. It is the most common tree found from Iceland, Scandinavia, North Russia and Alpes. Closely related species are found in East Asia, North America and South America (Andes). Silver birch in Scandinavia is considered the most important allergen of all, exceeding grass pollen in reactivity. Birch pollen is a major cause of allergic morbidity in northern Europe and in eastern parts of North America. Birch trees became very popular ornamental plants in parks and private gardens during the 1970s and 1980s, causing the appearance of, and a significant increase in, allergic sensitization to tree pollen allergens [1]. The marked difference in prevalence of birch pollen allergy in people attending allergy clinics in the area north of Milan, compared to those from the city of Milan (5 Km away) where birch trees have not been planted extensively, has been highlighted [2]. Pollination occurs from April to May. Studies of the different allergens in birch pollen indicate presence of major antigens which are also found in Oak, and possibly in other tree pollens. Bet v I is the major allergen birch pollen and Bet v II is its minor allergen (See Betula). In a multi-center study, comprising 16 clinics, 871 adult hay fever patients were studied. Most patients included had springtime hay fever. Skin prick tests were performed with 20 different tree or bush pollen (lignoses) allergens. RAST determination were done with eight different tree pollen allergens in 590 patients. Birch pollen (BP) allergen gave the highest frequency of positive tests results. The test results with the various tree pollen allergens in patients with BP allergy were compared with those in patients without BP allergy. With all the allergens a significantly higher frequency of positive test results was found in those with BP allergy than in those without. Only very small differences were  noted between various parts of the country, and sensitization against various tree pollens was common even in regions where the corresponding tree do not grow. It was concluded that a high degree of cross-sensitization exists among tree pollens, and testing with BP allergen is sufficient for the screening of tree pollen allergy [3]. Common silver birch is symbolized in RAST as t3.  Patients with birch or nasal pollen allergy should be asked about food hypersensitivity. The history of food hypersensitivity is of clinical value, and patients with hypersensitivity to nuts and apples are more allergic and need more effective treatment

than others [4]. In central and northern Europe, allergy to food of plant origin is mediated, in most instances, by sensitization to birch pollen, and up to 80% of birch pollen allergic patients suffer from an associated food allergy[5].. Patients sensitized to birch pollen are mainly affected by allergic reactions to foods of the Rosaceae family (such as apple, pear, cherry, peach and nectarine) and to various vegetables.

There was only very limited documentation of the efficacy and safety of high-dose subcutaneous birch pollen immunotherapy (IT) in double-blind, placebo-controlled (DBPC) studies. Bødtger et al (2002) demonstrated that high-dose, subcutaneous IT is efficacious and safe in patients with severe birch pollen rhinoconjunctivitis and asthma[6].

Birch pollen allergy was shown to be associated with changes in fecal microbiota composition. The specific combination of probiotics [Lactobacillus acidophilus (L. acidophilus) NCFM (ATCC 700396) and Bifidobacterium lactis (B. lactis) Bl-04 (ATCC SD5219)] used was shown to prevent the pollen-induced infiltration of eosinophils into the nasal mucosa, and indicated a trend for reduced nasal symptoms [7].

References

1. D'Amato G, Spieksma FThM, Liccardi G, Jager S, et al. Pollen-related allergy in Europe. Allergy 1998;53:567-578.

2. Asero R, Qualizza R, Schilke ML, Sillano V, Zanoletti T. Studio multicentrico sulla prevalenza delle pollinosi nella città e nella provincia di Milano: 1990-95. Giorn It Allergol Immunol Clin 1998;8:241 (abstract).

3. Eriksson N.E., Wihl J.A., Arrendal H., Strandhede S.O.: Tree Pollen Allergy, Allergy 1984, 39, 610-617.

4. Fogle - Hanson, M. Bende, M:  The significance of hypersensitivity to nuts in patients with birch pollen allergy. Allergy 1993:48: 282-284.

5. Johansson SGO, O'B Hourihane J, bousquet J et al. A revised nomenclature for allergy. An EAACI position statement from the EAACI nomenclature task force. Allergy 2001;56: 813-824.

6. Bødtger, U. et al: The safety and efficacy of subcutaneous birch pollen immunotherapy - a one-year, randomised, double-blind, placebo-controlled study Allergy2002: 57: 297

7. Ouwehand AC, Nermes M, Collado MC, Rautonen N, Salminen S, Isolauri E. Specific probiotics alleviate allergic rhinitis during the birch pollen season. World J Gastroenterol. 2009 Jul 14;15(26):3261-8.