Type:
Whole Allergen
Allergen Encyclopedia
Table of Contents
Whole Allergen
t25 European ash
t25 European ash Scientific Information
Display Name:
European ash
Route of Exposure:
Inhalation
Family:
Oleaceae
Species:
Fraxinus excelsior
Latin Name:
Fraxinus excelsior
Other Names:
Ash
Summary
European ash trees (Fraxinus excelsior) are distributed across temperate regions of Europe, North America and central Asia. Fraxinus pollen is a potent allergen source causing asthma, allergic rhinoconjunctivitis and potentially urticaria and allergic dermatitis. Ash pollen shares structural and allergenic similarities with other members of the Oleaceae (olive) family, although there is conflicting evidence for cross-reactivity with olive tree pollen.
Allergen
Nature
The European ash is a deciduous tree of temperate regions, widely distributed across most of Europe except northern Scandinavia and the southern Mediterranean (1). It is also found in North America and in central Asia, including central and southern Russia, Iran, Iraq and Turkey (2, 3).
Fraxinus pollen is wind-borne (2). Peak pollen counts are seen in April in the UK, with a medium-high emissions strength compared to other common tree pollens (4). In north-western Spain, Fraxinus flowers during the winter (December to March/early April) and ash pollen constitutes about 2% of total airborne pollen (5). In north-eastern Iran, ash was among the most prevalent aeroallergens seen in all seasons of the year (6). Ash was also the leading tree pollen allergen in a 2015 study of aeroallergens in Istanbul (7).
Fraxinus pollen counts fall during periods of rainfall and high humidity, when pollen grains are removed from the air to the ground. Fraxinus allergen concentrations correlate with high air temperature but also with rainfall, as the osmotic pressure of water tends to explode pollen grains, releasing submicronic protein particles into the atmosphere (5).
Taxonomy
Taxonomic tree of Fraxinus genus (2) |
|
Domain |
Eukaryota |
Kingdom |
Plantae |
Phylum |
Spermatophyta |
Subphylum |
Angioospermae |
Class |
Dicotyledonae |
Family |
Oleaceae |
Genus |
Fraxinus |
Tissue
Tree pollen.
Environmental Characteristics
Worldwide distribution
Fraxinus excelsior is a broad-leaved tree common in many types of forest throughout Europe. It has a high economic value due to its fast growth and outstanding wood properties (8). European ash is used as an ornamental tree in Spanish cities (9).
Route of Exposure
Main
The main route of exposure is inhalation.
Detection
Detection
Ash pollen is sampled using a vacuum air sampler such as the Burkard volumetric spore sampler (10) or the Hirst-type pollen trap (11).
Clinical Relevance
European ash is a potent allergen source (3) and a common cause of allergic rhinitis, conjunctivitis and asthma (6, 12). The prevalence of ash pollen sensitization in Germany is about 10%, although it may be underestimated because the ash pollination season in Europe overlaps with birch (Betulaceae) (13). In a study of 5416 Austrian patients sensitized to any pollen, 17.6% had a positive skin prick test to ash (14). In northern Iran, 36.7% of 1006 allergic patients showed a positive skin prick test to Fraxinus excelsior; this was significantly associated with asthma and allergic rhinitis, although urticaria and atopic dermatitis were also recorded (6). In a New York study, 27% of 371 allergic patients were sensitized to ash (3), while in Istanbul, 8.1% of 60 allergic patients showed a positive skin prick test to ash, which was the main sensitizer among the woody plants tested (7).
Allergic rhinitis
In a Belgian study comparing pollen exposure and sales of allergic rhinitis medication, positive associations were found between Fraxinus pollen counts and medication sales (10).
Other topics
In nasal provocation tests, 58% of 113 ash-sensitized patients showed symptoms of allergy, while 42% were clinically silent. 94% of sensitized patients and 88% of allergic patients were poly-sensitized to three or more allergens in addition to ash pollen, and 86% of all patients also had a positive skin prick test to birch (Betulaceae) pollen (13).
Diagnostics Sensitization
Testing ash sensitization using specific IgE to native ash extract is almost as effective as the skin prick test (SPT), with 98% of 113 SPT-positive patients showing specific IgE (13).
Prevention and Therapy
Allergen immunotherapy
One study suggests that better standardized or more widely available olive pollen extracts may be used instead of ash pollen extract for allergen-specific immunotherapy (12); this is not supported by a more recent study (13).
Prevention strategies
Avoidance
Allergenic vegetation maps may contribute to allergy risk assessments by showing the location of ash trees at 1 km resolution. They can be combined with health data to inform allergy research, or with weather data to improve pollen forecasting or to generate pollen emission models (4). Fraxinus allergy risk periods can also be forecasted using regression equations of pollen count, rainfall and temperature (5).
Molecular Aspects
Allergenic molecules
Allergenic molecules of Fraxinus excelsior (15-17)
Allergen name |
Biochemical name/protein group (where known) |
Fra e 1 |
Ole e 1-like protein family member |
Fra e 2 |
Profilin |
Fra e 3 |
Calcium-binding protein (polcalcin) |
Fra e 6 |
- |
Fra e 7 |
- |
Fra e 9 |
ß-1,3-Glucanase |
Fra e 11 |
- |
Fra e 12 |
- |
Fra e 1 is the major pollen allergen of Fraxinus excelsior. It belongs to the olive tree (Ole e 1) protein family and shows a high degree of homology with other Oleaceae proteins (3, 5). Fra e 1 exhibits 82%, 88%, and 91% amino acid sequence identity with lilac (Syr v 1), olive (Ole e 1), and privet (Lig v 1), respectively (3).
Cross-reactivity
Extensive immunological cross-reactivity between olive, ash and privet pollen may lead to poly-sensitization of susceptible patients due to the priming effect (5, 9). Cross-reactivity between the main allergens of Fraxinus and Olea species has been demonstrated by using Ole e 1 (olive) antibodies to detect Fra e 1 (ash) allergens in the atmosphere (9). One study found that determining specific IgE to Ole e 1 was as effective at diagnosing ash pollen allergy as determining IgE to Fra e 1 (Imhof et al. 2014), whereas another concluded that in countries where sensitization to ash does not occur via the olive tree, testing for component olive allergens (rOle e 1, nOle e 7, rOle e 9) will not reliably identify ash sensitization and allergy (13). There is very limited cross-reactivity between ash and birch pollen allergens (12).
Compiled By
Author: RubyDuke Communications
Reviewer: Dr. Christian Fischer
Last reviewed:February 2022
References
- LOINC. European Ash wood dust IgE Ab [Units/volume] in Serum 2021 [cited 2021 16.11.21]. Available from: https://loinc.org/96280-3/.
- CABI. Fraxinus excelsior (ash) Wallingford, UK2021 [cited 2021 16.11.21]. Available from: https://www.cabi.org/isc/datasheet/24522.
- Asam C, Hofer H, Wolf M, Aglas L, Wallner M. Tree pollen allergens-an update from a molecular perspective. Allergy. 2015;70(10):1201-11.
- McInnes RN, Hemming D, Burgess P, Lyndsay D, Osborne NJ, Skjøth CA, et al. Mapping allergenic pollen vegetation in UK to study environmental exposure and human health. Science of The Total Environment. 2017;599-600:483-99.
- Vara A, Fernández-González M, Aira MJ, Rajo FJ. Fraxinus pollen and allergen concentrations in Ourense (South-western Europe). Environmental Research. 2016;147:241-8.
- Mahboubi Oskouei Y, Farid Hosseini R, Ahanchian H, Jarahi L, Ariaee N, Jabbari Azad F. Report of Common Aeroallergens among Allergic Patients in Northeastern Iran. Iran J Otorhinolaryngol. 2017;29(91):89-94.
- Zemmer F, Cenk E, Dahl Å, Galan C, Ozkaragoz F. A multidisciplinary approach of outdoor aeroallergen selection for skin prick testing in the geographical area of Greater Istanbul. Eur Ann Allergy Clin Immunol. 2021.
- Dobrowolska D, Hein S, Oosterbaan A, Wagner S, Clark J, Skovsgaard JP. A review of European ash (Fraxinus excelsior L.): implications for silviculture. Forestry: An International Journal of Forest Research. 2011;84(2):133-48.
- Vara A, Fernández-González M, Aira MJ, Rodríguez-Rajo FJ. Oleaceae cross-reactions as potential pollinosis cause in urban areas. Sci Total Environ. 2016;542(Pt A):435-40.
- Guilbert A, Simons K, Hoebeke L, Packeu A, Hendrickx M, De Cremer K, et al. Short-Term Effect of Pollen and Spore Exposure on Allergy Morbidity in the Brussels-Capital Region. Ecohealth. 2016;13(2):303-15.
- Maya-Manzano JM, Sadyś M, Tormo-Molina R, Fernández-Rodríguez S, Oteros J, Silva-Palacios I, et al. Relationships between airborne pollen grains, wind direction and land cover using GIS and circular statistics. Sci Total Environ. 2017;584-585:603-13.
- Imhof K, Probst E, Seifert B, Regenass S, Schmid-Grendelmeier P. Ash pollen allergy: reliable detection of sensitization on the basis of IgE to Ole e 1. Allergo J Int. 2014;23(3):78-83.
- Eder K, Gellrich D, Meßmer C, Canis M, Gröger M. Component resolved analysis of ash pollen allergy in Bavaria. Allergy, Asthma & Clinical Immunology. 2018;14(1):76.
- Hemmer W, Focke M, Wantke F, Götz M, Jarisch R, Jäger S, et al. Ash (Fraxinus excelsior)-pollen allergy in central Europe: specific role of pollen panallergens and the major allergen of ash pollen, Fra e 1. Allergy. 2000;55(10):923-30.
- Mas S, Torres M, Garrido-Arandia M, Salamanca G, Castro L, Barral P, et al. Ash pollen immunoproteomics: identification, immunologic characterization, and sequencing of 6 new allergens. J Allergy Clin Immunol. 2014;133(3):923-6.e3.
- Torres M, Palomares O, Quiralte J, Pauli G, Rodríguez R, Villalba M. An Enzymatically Active β-1,3-Glucanase from Ash Pollen with Allergenic Properties: A Particular Member in the Oleaceae Family. PLOS ONE. 2015;10(7):e0133066.
- Matricardi PM, Kleine-Tebbe J, Hoffmann HJ, Valenta R, Hilger C, Hofmaier S, et al. EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol. 2016;27 Suppl 23:1-250.
