Grey alder

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Code: t2
Latin name: Alnus incana
Source material: Pollen
Family: Betulaceae
Common names: Grey alder, speckled alder

Allergen Exposure

The Fagales order consists of trees from the Betulaceae family (grey alder and birch tree), along with hazel, hornbeam, oak, and chestnut tree.

Grey alder is the most widely distributed alder in Europe and western North America.

Grey alder is a rapidly growing, deciduous, multi-stemmed shrub or small tree, which tends to form thickets. It has a long trunk and a narrow crown. The alder typically grows between 2 and 5 m in height, but may reach 12 m. The bark is thin, smooth, and green-grey, greyish-brown, or reddish-brown. Trees often produce adventitious roots from near the base of the stem. The leaves are broadly elliptic or ovate, and dull green on both sides. The leaves remain green until they are dropped in the autumn.

Flowering generally begins during March or April, with seeds ripening from September to November. The flowers occur in catkins and are monoecious (individual flowers are either male or female, but both sexes are found on the same plant). Alders are wind-pollinated, and produce clouds of yellow pollen. The cones remain on the plants for about a year after the seeds are shed, aiding in identification during winter. The fruit is a small, single-seeded nutlet, with narrow lateral wings.

Grey alder seldom grows at a distance from water. It is typically found bordering streams, rivers and mountain springs, on moist lowlands and in swamps. It invades gaps and clearings in forests and thrives there.

Allergen Description

More than 30 allergens have been detected in Alnus pollen, mainly from analysis of A. glutinosa. (1, 2, 3, 4, 5, 6)

No allergens have been characterised from grey alder tree (A. incana), but the following allergens have been characterised from A. glutinosa:

Aln g 1, a 17 kDa protein, a Bet v 1 homologue (Group 1 Fagales-related protein). (7, 8, 9, 10, 11, 12)

Aln g 2, a profilin. (13)

Aln g 4, a 9.4 kDa protein, a polcalcin, a calcium-binding protein. (12, 14, 15, 16)

Potential Cross-Reactivity

Extensive cross-reactivity between the different individual species of the genus (e.g. between A.incana and A. glutinosa) could be expected. (17)

The Fagales order consists of trees from the Betulaceae family (grey alder and birch tree), along with hazel, hornbeam, oak, and chestnut tree. It is widely accepted that Fagales pollen allergies are initiated by sensitisation against Bet v 1, the birch pollen major allergen. A study investigated the allergenic potential of the (clinically, most important) Fagales pollen allergens from birch, alder, hazel, hornbeam, hop-hornbeam, oak, beech and chestnut; and showed that all the allergens showed the typical Bet v 1-like secondary structure elements, and were all able to bind serum IgE from Fagales-allergic donors. The data suggested that Bet v 1-like allergens of the Betuloideae and Coryloideae subfamily (subfamilies of the Betulaceae family) might have the potential to induce IgE antibodies with different specificities, while allergic reactions towards Fagaceae allergens are the result of IgE cross-reactivity. (18)

Studies of cross-reactivity have mostly concerned A. glutinosa, but because of the close relationship between this species and A. incana, their cross-reactivity is most probably similar. Close cross-reactivity has been demonstrated between birch, alder and beech pollen, (19) as well as between birch, alder and hazel (as a result of the common Bet v 1 homologous allergens Aln g 1, Bet v 1 and Cor a 1). (7, 4, 9, 20, 21) Cross-reactivity has also been demonstrated among birch, alder, hornbeam, hazel, European chestnut and oak. (13, 22, 23) Aln g 1 and Bet v 1 from birch tree have an 86.8% homology. (8) Cor a 1 isoforms from hazel pollen have been reported to have a 75.5-76.7% identity (83.6-85% similarity) with Aln g 1. (24)

Alder tree contains a calcium-binding protein, which may result in cross-reactivity with other pollens containing calcium-binding protein, e.g. Timothy grass, rye grass, birch tree, olive tree, mugwort, and ragweed. (25)

Patients sensitised to Japanese hop pollen have been reported to have a higher prevalence of skin-prick tests for (among other pollens) those of sunflower, Bermuda grass, orchard grass, alder tree, birch tree, and poplar tree. (26)

Cross-reactivity between birch tree pollen and the fruit of kiwi has been suggested. The amino acid sequence identity between the kiwi allergens Act d 8 and Act c 8 was shown to be 70%, and to Bet v 1 53% and 54% respectively, suggesting that that Bet v 1 homologues are allergens in kiwifruit, and of relevance for patients sensitised to tree pollen and kiwifruit. Act d 8 and Act c 8 were shown to have 50% and 51% homology with the Bet v 1 homologues in Aln g 1 from alder. (27)

Clinical Experience

IgE mediated reactions

Fagales pollen allergy represents the main cause of winter/spring pollinosis in the temperate climate zone of the Northern hemisphere. (18) Alder pollen (a member of the Fagales order) is a significant cause of asthma, allergic rhinitis and allergic conjunctivitis, in particular in springtime in middle and northern Europe, and in conjunction with birch and hazel pollen. (28, 29, 30, 31, 32, 33) The majority of studies have assessed either the Alnus species in general or A. glutinosa specifically; however, the close relationship between A. incana and other Alnus species, including A. glutinosa, suggests that a number of inferences can be drawn.

Allergy to alder is important in northern European countries and is increasing in southern Europe. Alder has been reported to be a significant cause of sensitisation or allergy in a wide range of geographic locations, including Genoa (a northern Mediterranean area in Italy), (33) southern Finland, (34) Fairbanks, Alaska, (35) Spain, (36, 37, 38) Norway, (39) Australia, (39) and Switzerland. (40, 41) In central Italy, the pollination period stretches from February to mid-October. Pollen count from alder is particularly high in the month of March. (42) Alder has also been reported to be relevant in Japan; (43, 44) however, Alnus sieboldiana Matsumura may be the predominant species. (45)

Studies have reported on alder pollen in Warsaw, Poland, (46) Sweden,  (31) the Philippines, (47) and Tehran, Iran. (48) In Plasencia, Spain, Alnus was the eighth-most-prominent pollen found in an aerobiological study. Of 210 patients with a diagnosis of pollinosis, 20.9% were sensitised to Alnus glutinosa. (49) Alder pollen has been documented in aerobiological studies in Worcester, in the West Midlands, United Kingdom, (50) and in Rochester, Minnesota, USA. (51)

In an ‘All India Coordinated Project on Aeroallergens and Human Health’ study evaluating the prevalence of pollen allergens at 18 different centres in the country, the allergenically important pollens included Alnus. (52) However, in India a number of other Alnus species occur, including Alnus nitida, an important sensitiser in Delhi patients. (53)

As the amount of measurable pollen is highly dependent on geographic and climatic conditions, it varies considerably between different regions of a country, as documented in Switzerland, as well as between different countries and continents. (54) In the southern part of Switzerland, of 503 patients with allergic rhinitis tested by skin-prick for sensitisation to common allergens, 33% were sensitised to alder tree pollen. (29)

A study determined the impact of different trees on asthma and explored the association between daily hospitalisations for asthma and daily concentrations of different tree pollens in 10 large Canadian cities. In correlating interquartile increases in daily tree pollen concentration with percentage increases in daily hospitalisation for asthma, a statistically significant but small (<2%) effect was observed for Alnus. (55)

In Poznań, Poland, symptoms of patients with positive skin-prick tests to Alnus pollen allergens were the following: 51% pollinosis, 43% atopic dermatitis, 4% asthma, 1% chronic urticaria and 1% eczema. Serum-specific IgE for Alnus was class 5 or 6 in 21%. The authors considered that Alnus pollen is generally mildly allergenic, but that the amount of Alnus pollen released into the atmosphere in places such as Poznań may increase its impact on the population and make it one of the more important aeroallergens present. (56)

Alder pollen was reported to be a significant aeroallergen in Zagreb, Croatia. Patients with monosensitisation to birch pollen had the most severe symptoms in April. In the patients with poylsensitisation to alder, hazel and birch pollen who were cross-reactive, initial symptoms occurred as early as February, with abrupt exacerbation in March and April. The most severely affected patients were those allergic to birch, hazel, alder, grass and ragweed pollen, who had symptoms throughout the year, with exacerbation in spring and the late summer months. (57)

Compiled by Dr Harris Steinman,


  1. Hemmens VJ, Baldo BA, Bass D, Vik H, Florvaag E, Elsayed S. A comparison of the antigenic and allergenic components of birch and Alder pollens in Scandinavia and Australia. Int Arch Allergy Appl Immunol 1988;85(1):27-37.
  2. Wiebicke K, Schlenvoigt G, Jäger L. Allergologic-immunochemical study of various tree pollens. I. Characterization of antigen and allergen components in birch, beech, alder, hazel and oak pollens. [German] Allerg Immunol (Leipz) 1987;33(3):181-90.
  3. Florvaag E, Elsayed S, Hammer AS. Comparative studies on tree pollen allergens. XIII. Partial characterization of the Alder (Alnus incana) pollen extract by two-dimensional IEF/SDS-PAG electrophoresis combined with electrophoretic transfer and immunoautoradiography. Int Arch Allergy Appl Immunol 1986;80(1):26-32.
  4. Ipsen H, Bøwadt H, Janniche H, Nüchel Petersen B, Munch EP, Wihl JA, Løwenstein H. Immunochemical characterization of reference alder (Alnus glutinosa) and hazel (Corylus avellana) pollen extracts and the partial immunochemical identity between the major allergens of alder, birch and hazel pollens. Allergy 1985;40(7):510-8.
  5. Florvaag E, Elsayed S. Comparative studies on tree pollen allergens. VIII. Immunological properties of the Alder (Alnus incana) pollen extract. Int Arch Allergy Appl Immunol 1984;75(4):300-8.
  6. Florvaag E, Elsayed S, Apold J. Comparative studies on tree pollen allergens. II. Isolation of Alder (Alnus incana) pollen allergens: purification and some characteristics of the major allergen pI 4.78. Int Arch Allergy Appl Immunol 1982;67(1):49-56.
  7. Ebner C, Ferreira F, Hoffmann K, Hirschwehr R, Schenk S, Szépfalusi Z, Breiteneder H, Parronchi P, Romagnani S, Scheiner O, et al. T cell clones specific for Bet v I, the major birch pollen allergen, crossreact with the major allergens of hazel, Cor a I, and alder, Aln g I. Mol Immunol 1993;30(15):1323-9.
  8. Breiteneder H, Ferreira F, Reikerstorfer A, Duchene M, Valenta R, Hoffmann-Sommergruber K, Ebner C, Breitenbach M, Kraft D, Scheiner O. Complementary DNA cloning and expression in Escherichia coli of Aln g I, the major allergen in pollen of alder (Alnus glutinosa). J Allergy Clin Immunol 1992;90(6 Pt 1):909-17.
  9. Ipsen H, Wihl JA, Petersen BN, Løwenstein H. Specificity mapping of patients IgE response towards the tree pollen major allergens Aln g I, Bet v I and Cor a I. Clin Exp Allergy 1992;22(3):391-9.
  10. Valenta R, Breiteneder H, Petternburger K, Breitenbach M, Rumpold H, Kraft D, Scheiner O. Homology of the major birch-pollen allergen, Bet v I, with the major pollen allergens of alder, hazel, and hornbeam at the nucleic acid level as determined by cross-hybridization. J Allergy Clin Immunol 1991;87(3):677-82.
  11. Rohac M, Birkner T, Reimitzer I, Bohle B, Steiner R, Breitenbach M, Kraft D, Scheiner O, Gabl F, Rumpold H. The immunological relationship of epitopes on major tree pollen allergens. Mol Immunol 1991;28(8):897-906.
  12. International Union of Immunological Societies Allergen Nomenclature: IUIS official list Accessed February 2013.
  13. Niederberger V, Pauli G, Grönlund H, Fröschl R, Rumpold H, Kraft D, Valenta R, Spitzauer S. Recombinant birch pollen allergens (rBet v 1 and rBet v 2) contain most of the IgE epitopes present in birch, alder, hornbeam, hazel, and oak pollen: a quantitative IgE inhibition study with sera from different populations. J Allergy Clin Immunol 1998;102(4 Pt 1):579-91.
  14. Wopfner N, Dissertori O, Ferreira F, Lackner P. Calcium-binding proteins and their role in allergic diseases. Immunol Allergy Clin North Am 2007;27(1):29-44.
  15. Tinghino R, Twardosz A, Barletta B, Puggioni EM, Iacovacci P, Butteroni C, Afferni C, Mari A, Hayek B, Di Felice G, Focke M, Westritschnig K, Valenta R, Pini C. Molecular, structural, and immunologic relationships between different families of recombinant calcium-binding pollen allergens. J Allergy Clin Immunol 2002;109(2 Pt 1):314-20.
  16. Hayek B, Vangelista L, Pastore A, Sperr WR, Valent P, Vrtala S, Niederberger V, Twardosz A, Kraft D, Valenta R. Molecular and immunologic characterization of a highly cross-reactive two EF-hand calcium-binding alder pollen allergen, Aln g 4: structural basis for calcium-modulated IgE recognition. J Immunol 1998;161(12):7031-9.
  17. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
  18. Hauser M, Asam C, Himly M, Palazzo P, Voltolini S, Montanari C, Briza P, Bernardi ML, Mari A, Ferreira F, Wallner M. Bet v 1-like pollen allergens of multiple Fagales species can sensitize atopic individuals. Clin Exp Allergy 2011;41(12):1804-14.
  19. Maeda Y, Ono E, Fukutomi Y, Taniguchi M, Akiyama K. Correlations between Alder specific IgE and Alder-related tree pollen specific IgE by RAST method. Allergol Int 2008;57(1):79-81.
  20. Van Ree R, Van Leeuwen WA, Akkerdaas JH, Aalberse RC. How far can we simplify in vitro diagnostics for Fagales tree pollen allergy? A study with three whole pollen extracts and purified natural and recombinant allergens. Clin Exp Allergy 1999;29(6):848-55.
  21. Maguchi S, Takagi S, Yoshida M, Fukuda S, Inuyama Y. Birch pollen nasal allergy in Sapporo and its cross reactivity with alder pollen. [Japanese] Nippon Jibiinkoka Gakkai Kaiho 1993;96(1):1-9.
  22. Hoffmann-Sommergruber K, Susani M, Ferreira F, Jertschin P, Ahorn H, Steiner R, Kraft D, Scheiner O, Breiteneder H. High-level expression and purification of the major birch pollen allergen, Bet v 1. Protein Expr Purif 1997;9(1):33-9.
  23. Kos T, Hoffmann-Sommergruber K, Ferreira F, Hirschwehr R, Ahorn H, Horak F, Jager S, Sperr W, Kraft D, Scheiner O. Purification, characterization and N-terminal amino acid sequence of a new major allergen from European chestnut pollen--Cas s 1. Biochem Biophys Res Commun 1993;15;196(3):1086-92.
  24. Breiteneder H, Ferreira F, Hoffmann-Sommergruber K, Ebner C, Breitenbach M, Rumpold H, Kraft D, Scheiner O. Four recombinant isoforms of Cor a I, the major allergen of hazel pollen, show different IgE-binding properties. Eur J Biochem 1993;212(2):355-62.
  25. Grote M, Westritschnig K, Valenta R. Immunogold electron microscopic localization of the 2 EF-Hand calcium-binding pollen allergen Phl p 7 and its homologues in pollens of grasses, weeds and trees. Int Arch Allergy Immunol 2008;146(2):113-21.
  26. Park HS, Jung KS, Jee SY, Hong SH, Kim HY, Nahm DH. Are there any links between Hop Japanese pollen and other weed pollens or food allergens on skin prick tests? Allergy Asthma Proc 2001;22(1):43-6.
  27. Oberhuber C, Bulley SM, Ballmer-Weber BK, Bublin M, Gaier S, DeWitt AM, Briza P, Hofstetter G, Lidholm J, Vieths S, Hoffmann-Sommergruber K. Characterization of Bet v 1-related allergens from kiwifruit relevant for patients with combined kiwifruit and birch pollen allergy. Mol Nutr Food Res 2008;52 Suppl 2:S230-40.
  28. Wüthrich B, Annen H. Pollionosis: I. Findings on the clinical aspects and the pollen spectrum in 1565 pollen-sensitive patients. [German] Schweiz Med Wochenschr 1979;109(33):1212-8.
  29. Gilardi S, Torricelli R, Peeters AG, Wüthrich B. Pollinosis in Canton Ticino. A prospective study in Locarno. [German] Schweiz Med Wochenschr 1994;124(42):1841-7.
  30. Jung K, Schlenvoigt G, Jäger L. Allergologic-immunochemical study of tree and bush pollen. II--Study of the sensitization spectrum of patients with seasonal rhinitis in the spring. [German] Allerg Immunol (Leipz) 1987;33(4):215-21.
  31. Eriksson NE. Allergy to pollen from different deciduous trees in Sweden. An investigation with skin tests, provocation tests and the radioallergosorbent test (RAST) in springtime hay fever patients. Allergy 1978;33(6):299-309.
  32. Piotrowska K. Comparison of Alnus, Corylus and Betula pollen counts in Lublin (Poland) and Skien (Norway). Ann Agric Environ Med 2004;11(2):205-8.
  33. Troise C, Voltolini S, Delbono G, Negrini AC. Allergy to pollens from Betulaceae and Corylaceae in a Mediterranean area (Genoa, Italy)--a ten-year retrospective study. J Investig Allergol Clin Immunol 1992;2(6):313-7.
  34. Koivikko A, Kupias R, Mäkinen Y, Pohjola A. Pollen seasons: forecasts of the most important allergenic plants in Finland. Allergy 1986;41(4):233-42.
  35. Anderson JH. A survey of allergenic airborne pollen and spores in the Fairbanks area, Alaska. Ann Allergy 1984;52(1):26-31.
  36. Silva Palacios I, Tormo Molina R, Nuñoz Rodríguez AF. Influence of wind direction on pollen concentration in the atmosphere. Int J Biometeorol 2000;44(3):128-33.
  37. Hernández Prieto M, Lorente Toledano F, Romo Cortina A, Dávila González I, Laffond Yges E, Calvo Bullón A. Pollen calendar of the city of Salamanca (Spain). Aeropalynological analysis for 1981-1982 and 1991-1992. Allergol Immunopathol (Madr) 1998;26(5):209-22.
  38. Rodriguez-Rajo FJ, Dopazo A, Jato V. Environmental factors affecting the start of pollen season and concentrations of airborne Alnus pollen in two localities of Galicia (NW Spain). Ann Agric Environ Med 2004;11(1):35-44.
  39. Hemmens VJ, Baldo BA, Elsayed S, Bass D. Allergic response to birch and alder pollen allergens influenced by geographical location of allergic subjects. Int Arch Allergy Appl Immunol 1988;87(3):321-8.
  40. Schmid-Grendelmeier P. Pollen as the cause of allergies. [German] Ther Umsch 2001;58(5):285-91.
  41. Helbling A, Leuschner RM, Wüthrich B. Pollinosis. IV. Which pollens should be tested in allergology practice? Results of determinations of allergy-causing pollens in the Zurich air 1981-1984, with reference to threshold concentrations. [German] Schweiz Med Wochenschr 1985;115(34):1150-9.
  42. Murgia M, De Dominicis V, Cresti M. The pollen calendar of Siena (Central Italy). Allergol Immunopathol (Madr) 1983;11(5):361-5.
  43. Sugii K, Tachimoto H, Syukuya A, Suzuki M, Ebisawa M. Association between childhood oral allergy syndrome and sensitization against four major pollens (Japanese cedar, orchard grass, short ragweed, alder). [Japanese] Arerugi 2006;55(11):1400-8.
  44. Wagatsuma Y, Kishikawa R, Matsumoto S. Pollen surveys in Sapporo for 6 years during 1992 to 1997. [Japanese] Arerugi 2001;50(5):467-72.
  45. Nakahara T, Ashida T, Etoh Y, Yoshikawa T, Ide T, Tabata S. A case of Alder (Alnus sieboldiana) pollinosis and its prevalence among the residents of a densely forested area. [Japanese] Arerugi 1990;39(2 Pt 1):104-9.
  46. Weryszko-Chmielewska E, Puc M, Rapiejko P. Comparative analysis of pollen counts of Corylus, Alnus and Betula in Szczecin, Warsaw and Lublin (2000-2001). Ann Agric Environ Med 2001;8(2):235-40.
  47. Cua-Lim F, Payawal PC, Laserna G. Studies on atmospheric pollens in the Philippines. Ann Allergy 1978;40(2):117-23.
  48. Shafiee A. Atmospheric pollen counts in Tehran, Iran, 1974. Pahlavi Med J 1976;7(3):344-51.
  49. Cosmes Martín PM, Moreno Ancillo A, Domínguez Noche C, Gutiérrez Vivas A, Belmonte Soler J, Roure Nolla JM. Sensitization to Castanea sativa pollen and pollinosis in northern Extremadura (Spain). [Spanish] Allergol Immunopathol (Madr ) 2005;33(3):145-50.
  50. Emberlin J, Smith M, Close R, Adams-Groom B. Changes in the pollen seasons of the early flowering trees Alnus spp. and Corylus spp. in Worcester, United Kingdom, 1996-2005. Int J Biometeorol 2007;51(3):181-91.
  51. Decco ML, Wendland BI, O'Connell EJ. Volumetric assessment of airborne pollen and spore levels in Rochester, Minnesota, 1992 through 1995. Mayo Clin Proc 1998;73(3):225-9.
  52. Singh AB, Kumar P. Aeroallergens in clinical practice of allergy in India. An overview. Ann Agric Environ Med 2003;10(2):131-6.
  53. Bist A, Kumar L, Roy I, Ravindran P, Gaurs SN, Singh AB. Clinico-immunologic evaluation of allergy to Himalayan tree pollen in atopic subjects in India--a new record. Asian Pac J Allergy Immunol 2005;23(2-3):69-78.
  54. Schmid-Grendelmeier P. Pollinosis: clinical aspects and epidemiology. Contribution of the Allergy Clinic 1948-1998. [German] Praxis (Bern 1994) 1998;87(40):1300-8.
  55. Dales RE, Cakmak S, Judek S, Coates F. Tree pollen and hospitalization for asthma in urban Canada. Int Arch Allergy Immunol 2008;146(3):241-7.
  56. Smith M, Emberlin J, Stach A, Czarnecka-Operacz M, Jenerowicz D, Silny W. Regional importance of Alnus pollen as an aeroallergen: a comparative study of Alnus pollen counts from Worcester (UK) and Poznań (Poland). Ann Agric Environ Med 2007;14(1):123-8.
  57. Peternel R, Milanović SM, Hrga I, Mileta T, Culig J. Incidence of Betulaceae pollen and pollinosis in Zagreb, Croatia, 2002-2005. Ann Agric Environ Med 2007;14(1):87-91.


As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.