Maple leaf sycamore, London plane

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Code: t11
Latin name: Platanus acerifolia
Source material: Pollen
Family: Platanaceae
Common names: Maple leaf sycamore, London plane tree, American sycamore

Synonyms: P. hispanica, P. hybrida

This is a somewhat variable species. It is often considered to be a hybrid of P. orientalis and P. occidentalis.

Not to be confused with the Maple tree (Acer spp.), i.e. Box-elder (A. negundo)

Allergen Exposure

Geographical distribution
The London plane, easily recognised by the bark, which exfoliates in large flakes, is renowned as a street tree, particularly in Europe. The origin of this hybrid is uncertain. It is found planted from southern and central Europe to western Asia, North America, South Africa, Australia and New Zealand, especially in urban areas. In America the tree probably crossed with a native variety and thus looks different from the European species. Over half of the trees on London streets are Plane trees, and Philadelphia has over 500,000.

The London plane is a large deciduous tree in a spreading form, with heavy, slightly drooping branches, reaching 21 – 30 m in height, and normally with a single stem clear of branches to a considerable height. The bark is mottled cream, grey, olive, and light-brown and usually but not always flakes in patches, creating a dappled appearance. The trunk may look rugged.

The triangular-ovate ”maple-like” leaf is medium- to dark-green, paler on the underside, and mat to glossy on the top. The leaves turn yellow-brown in autumn.

The green flowers are monoecious (individual flowers are either male or female, but both sexes can be found on the same plant) and appear in April in the Northern Hemisphere. The tree is wind-pollinated, and the pollen is thought to be very allergenic.

The seeds/fruits are syncarps of achenes, about 2.5 cm in diameter. They change from green to brown in October and persist into winter.

The tree is found in woodland and gardens and lining streets.

Allergens of  17-18 kDa, 22 kDa, 43 kDa and 52 kDa have been isolated (1-4). The 17-18 kDa protein has been identified as Pla a 1 and appears to be a major allergen (3). The 43 kDa protein, now identified as Pla a 2, and the 52 kDa one were found to have IgE-binding prevalences of 83 and 42%, respectively (4).

To date, the following allergens have been characterised:
  • Pla a 1, an 18 kDa protein, an invertase inhibitor (5-8).
  • Pla a 2, a 43 kDa protein, a polygalacturonase (4,6,9).
  • Pla a 3, a 10 kDa lipid transfer protein (4,10).
  • Pla a Profilin (5,11-12).

Pla a 1 is recognised by up to 92% of monosensitised London plane tree-allergic patients and 83% of polysensitised patients (4,7).

Pla a 2 is involved in the allergic responses of 84% of patients with London plane tree pollen allergy and represents 52% of the total IgE-binding capacity of London plane tree extract (9).

In the Mediterranean area, Pla a 3 is a minor allergen (27.3%) in London plane pollen-allergic patients without food allergy, and a major allergen (63.8%) in London plane pollen-allergic patients with Peach allergy (10).

Potential cross-reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected (13).

Pla a 3, a lipid transfer protein, is a major cross-reactive allergen in Plane pollen-allergic patients with Peach allergy (10).

Other studies have indicated cross-reactivity between London plane pollen and food, but the cross-reactive allergen was not described. In a study of 56 patients allergic to food, skin prick tests demonstrated a positive correlation between London plane pollen and Hazelnut, Peanut, Banana and Celery. Inhibition studies confirmed strong cross-reactivity between London plane pollen and Hazelnut and Banana, and intermediate cross-reactivity with Celery and Peanut (14).

Similarly, in a study assessing the possible association of oral allergy syndrome with London plane tree pollen allergy, of 720 patients evaluated, 61 (8.48%) were sensitised to pollen from this tree. Food allergy was observed in 32 (52.45%) of the 61 patients sensitised to this tree’s pollen. The food allergens most frequently implicated were Hazelnut, Peach, Apple, Peanut, Maize, Chick pea and Lettuce. The authors suggested that oral allergy syndrome in these patients may have been caused by primary respiratory sensitisation to London plane tree pollen, and that profilin may be the responsible allergen (15).

More recently, IgE reactivity to profilin was studied using a pool of sera from 23 patients with London plane pollen allergy and food allergy. Inhibition assays conducted with Hazelnut, Apple peel, Peanut, Chick pea and Peanut extracts demonstrated cross-reactivity, but neither the profilin nor Pla a 1 nor Pla a 2 could explain the strong cross-reactivity demonstrated (11).

Further evidence for cross-reactivity between London plane tree pollen and foods was that London plane tree-specific immunotherapy resulted in a significant decrease in food allergy in 16 adult patients with allergy to Hazelnut, Walnut, Lettuce, Peach, Cherry and London plane tree pollen (16).

In a study of individuals presenting for the first time to any of the 6 allergy clinics in Spain with respiratory and/or cutaneous symptoms, among 1,734 individuals, the prevalence of sensitisation to Tomato was found to be 6.52% (113 patients). Of these Tomato-sensitised subjects, only 16% reported symptoms with Tomato, but 97% were sensitised to inhalant aeroallergens, including 84% to pollens (mainly Artemisia vulgaris and Platanus hybrida), with differences in the average profiles between Northern and Southern clinics. Most of the sensitised subjects were asymptomatic, but some patients reported symptoms although they had no skin test sensitivity (17).

A polygalacturonase was isolated from Lily pollen and displayed significant similarity to allergens in other plants, including Phl p 13 of Timothy grass and Pla a 2 of London plane tree (18).

Cannabis sativa leaf extract has been shown to share a degree of cross-reactivity with Tomato, Peach and Mugwort, and a lesser degree with London plane tree pollen (19).

Clinical Experience

IgE-mediated reactions
Plane trees are an important source of airborne allergens in many cities of the United States and Western Europe (7). and exposure to London plane tree pollen can induce asthma, allergic rhinitis and allergic conjunctivitis (20-22); systemic reactions have occurred during immunotherapy (23).

Initially, London plane tree pollen was not thought to contribute much to the prevalence of atopic sensitisation, even though the pollen had been detected in the atmosphere, but recent studies have shown that pollen from this tree is an important cause of pollinosis.

In a study in Madrid, Spain, among 187 patients with a history of rhinitis and/or seasonal asthma, a 56% prevalence of positive skin-prick tests to Platanus was found, surpassed (not necessarily in this order) only by the effects of pollen from the grasses Dactylis glomerata (Cocksfoot), Trisetum paniceum (Common wild oats) (92%), and Olive tree (63%). Aerobiological sampling of the pollen content of the air in Madrid revealed that 14.9% of this content consisted of Platanus. Specific IgE confirmed sensitisation to this allergen (24).

In an earlier study in Madrid, among 47 patients with spring-summer pollinosis symptoms who were seen at an allergy clinic, skin-prick tests to Platanus were positive in 33 of the 39 patients first seen with seasonal symptoms during Platanus pollen season, and only in 3 of the 8 patients without symptoms during Platanus exposure. Twenty-two of the 33 Platanus-positive skin-test patients also had a positive ELISA result. The average 24-hour rhinitis symptom scores of the 39 patients first seen with seasonal symptoms from March through April showed significant correlation with Platanus pollen counts. (3) The authors concluded that Platanus pollen was an important cause of pollinosis in this area.

High levels or this aeroallergen and its clinical importance have also been demonstrated in studies from Cape Town, South Africa, where Platanus pollen is abundant in September (25), from Zurich, Switzerland (26), from Balikesir, Turkey (27), and from Salamanca, Spain (28). Pollen from this tree was also demonstrated to be an important aeroallergen in Montpellier, in southern France, where the highest prevalence of allergy was to grass pollen, followed by Plantain, Parietaria, Oleaceae, London plane and Cupressaceae pollen; the prevalence of sensitisation among the entire group ranged from 13% to 36% of pollen-allergic patients (29).

In Plasencia, Spain, where Castanea sativa (European chestnut tree) is a major source of pollen, it was nevertheless demonstrated that of 210 patients with pollen allergy, 36.6 % were sensitised to Platanus acerifolia (30). In a study of 371 skin prick-tested paediatric patients in Cova da Beira, an interior region of Portugal, 11.4% were found positive for Platanus acerifolia (31). In Madrid, Spain, the second-most-abundant airborne aeroallergen, after pollen of Quercus spp., was pollen from Platanus spp. In skin prick tests, the prevalence of positive reactions to London plane tree pollen was 52% (32). London plane tree pollen was also reported to be an important aeroallergen in Seville, Spain (33).

Importantly, London plane-allergic individuals may be concomitantly allergic to foods (11,15). (See Potential cross-reactivity above.)

Other reactions
Allergic contact dermatitis from contact with the London plane tree has also been reported (34).

Compiled by Dr Harris Steinman,


  1. Anfosso F, Soler M, Mallea M, Charpin J. Isolation and characterization in vitro of an allergen from plane-tree (Platanus acerifolia) pollen. Int Arch Allergy Appl Immunol 1977;54(6):481-6
  2. Anfosso F, Leyris R, Charpin J. The allergen of plane-tree pollen. Characterization of a major allergen. Allergy 1980;35(3):196-8
  3. Varela S, Subiza J, Subiza JL, Rodriguez R, Garcia B, Jerez M, Jimenez JA, Panzani R. Platanus pollen as an important cause of pollinosis. J Allergy Clin Immunol 1997;100(6 Pt 1):748-54
  4. Asturias JA, Ibarrola I, Bartolome B, Ojeda I, Malet A, Martinez A. Purification and characterization of Pla a 1, a major allergen from Platanus acerifolia pollen. Allergy 2002;57(3):221-7
  5. International Union of Immunological Societies Allergen Nomenclature: IUIS official list 2008
  6. Asturias JA, Ibarrola I, Amat P, Tella R, Malet A, Cistero-Bahima A, Enrique E, Malek T, Martinez A. Purified allergens vs. complete extract in the diagnosis of plane tree pollen allergy. Clin Exp Allergy 2006;36(12):1505-12
  7. Asturias J, Ibarrola I, Eraso E, Arilla M, Martinez A. The major Platanus acerifolia pollen allergen Pla a 1 has sequence homology to invertase inhibitors. Clin Exp Allergy 2003;33(7):978-85
  8. Arilla MC, Ibarrola I, Mir A, Monteseirin J, Conde J, Martinez A, Asturias JA. Development of a Sandwich-Type ELISA for Measuring Pla a 1, the major allergen of Platanus acerifolia pollen. Int Arch Allergy Immunol 2005;138(2):2-133
  9. Ibarrola I, Arilla MC, Martnez A, Asturias JA. Identification of a polygalacturonase as a major allergen (Pla a 2) from Platanus acerifolia pollen. J Allergy Clin Immunol 2004;113(6):1185-91
  10. Lauer I, Miguel-Moncin MS, Abel T, Foetisch K, Hartz C, Fortunato D, Cistero-Bahima A, Vieths S, Scheurer S. Identification of a plane pollen lipid transfer protein (Pla a 3) and its immunological relation to the peach lipid-transfer protein, Pru p 3. Clin Exp Allergy 2007;37(2):261-9
  11. Enrique E, Alonso R, Bartolome B, San Miguel-Moncin M, Bartra J, Fernandez-Parra B, Tella R, Asturias JA, Ibarrola I, Martinez A, Cistero-Bahima A. IgE reactivity to profilin in Platanus acerifolia pollen-sensitized subjects with plant-derived food allergy. J Investig Allergol Clin Immunol 2004;14(4):4-342
  12. Barderas R, Villalba M, Rodriguez R. Recombinant expression, purification and cross-reactivity of chenopod profilin: rChe a 2 as a good marker for profilin sensitization. Biol Chem 2004;385(8):731-7
  13. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
  14. Miralles JC, Caravaca F, Guillen F, Lombardero M, Negro JM. Cross-reactivity between Platanus pollen and vegetables. Allergy 2002;57(2):146-9
  15. Enrique E, Cistero-Bahima A, Bartolome B, Alonso R, San Miguel-Moncin MM, Bartra J, Martinez A. Platanus acerifolia pollinosis and food allergy. Allergy 2002;57(4):351-6
  16. Alonso R, Enrique E, Pineda F, Basagaña M, San Miguel-Moncín MM, Bartra J, Palacios R, Cisteró-Bahíma A. An observational study on outgrowing food allergy during non-birch pollen-specific, subcutaneous immunotherapy. Int Arch Allergy Immunol 2007;143(3):185-9
  17. Larramendi CH, Ferrer A, Huertas AJ, Garcia-
    Abujeta JL, Andreu C, Tella R, Cerda MT, et al. Sensitization to tomato peel and pulp extracts in the Mediterranean Coast of Spain: prevalence and co-sensitization with aeroallergens. Clin Exp Allergy 2008;38(1):169-77
  18. Chiang JY, Shu SW, Ko CW, Wang CS. Biochemical characterization of a pollen-specific cDNA encoding polygalacturonase in Lilium longiflorum. Plant Sci 2006;170(3):433-40
  19. de Larramendi CH, Carnes J, Garcia-Abujeta JL, Garcia-Endrino A, Munoz-Palomino E, Huertas AJ, Fernandez-Caldas E, Ferrer A. Sensitization and allergy to Cannabis sativa leaves in a population of tomato (Lycopersicon esculentum)-sensitized patients. Int Arch Allergy Immunol 2008;146(3):195-202
  20. Bousquet J, Hejjaoui A, Becker WM, Cour P, Chanal I, Lebel B, et al. Clinical and immunologic reactivity of patients allergic to grass pollens and to multiple pollen species. I. Clinical and immunologic characteristics. J Allergy Clin Immunol 1991;87(3):737-46
  21. Carretero Anibarro P, Juste Picon S, Garcia Gonzalez F, Alloza Gomez P, Perez Jimenez R, Blanco Carmona J, Reinares Ten C, Vicente Serrano J, Bascones O. Allergenic pollens and pollinosis in the city of Burgos.
    Alergol Inmunol Clin 2005;20(3):90-4
  22. Belver MT, Caballero MT, Contreras J, Cabañas R, Sierra E, Madero R, López Serrano MC. Associations among pollen sensitizations from different botanical species in patients living in the northern area of Madrid. J Investig Allergol Clin Immunol 2007;17(3):157-9
  23. Hejjaoui A, Ferrando R, Dhivert H, Michel FB, Bousquet J. Systemic reactions occurring during immunotherapy with standardized pollen extracts. J Allergy Clin Immunol 1992;89(5):925-33
  24. Subiza J, Cabrera M, Valdivieso R, Subiza JL, Jerez M, Jimenez JA, Narganes MJ, Subiza E. Seasonal asthma caused by airborne Platanus pollen. Clin Exp Allergy 1994;24(12):1123-9
  25. Potter PC, Berman D, Toerien A, Malherbe D, Weinberg EG. Clinical significance of aero-allergen identification in the western Cape. S Afr Med J 1991;79(2):80-4
  26. Helbling A, Leuschner RM, Wuthrich 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
  27. Bicakci A, Akyalcin H. Analysis of airborne pollen fall in Balikesir, Turkey, 1996-1997. Ann Agric Environ Med 2000;7(1):5-10
  28. Hernandez Prieto M, Lorente Toledano F, Romo Cortina A, Davila Gonzalez I, Laffond Yges E, Calvo Bullon 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
  29. Bousquet J, Cour P, Guerin B, Michel FB. Allergy in the Mediterranean area. I. Pollen counts and pollinosis of Montpellier. Clin Allergy 1984;14(3):249-58
  30. Cosmes MP, Moreno AA, Dominguez NC, Gutierrez VA, Belmonte SJ, Roure NJ. Sensitization to Castanea sativa pollen and pollinosis in northern Extremadura (Spain). [Spanish] Allergol Immunopathol (Madr ) 2005;33(3):3-150
  31. Loureiro G, Rabaca M, Blanco B, Andrade S, Chieira C, Pereira C. Aeroallergens sensitization in an allergic paediatric population of Cova da Beira, Portugal. Allergol Immunopathol (Madr ) 2005;33(4):192-8
  32. Subiza J, Jerez M, Jimenez JA, Narganes MJ, Cabrera M, Varela S, Subiza E. Allergenic pollen pollinosis in Madrid. J Allergy Clin Immunol 1995;96(1):15-23
  33. Gonzalez Minero FJ, Candau P, Tomas C, Morales J. Daily variation patterns of airborne allergenic pollen in southwestern Spain. J Investig Allergol Clin Immunol 1998;8(2):89-93
  34. Poljacki M, Paravina M, Jovanovic M, Subotic M, Duran V. Contact allergic dermatitis caused by plants. [Serbo-Croatian] Med Pregl 1993;46(9-10):371-5


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