Type:
Whole Allergen
Allergen Encyclopedia
Table of Contents
Whole Allergen
t12 Willow
t12 Willow Scientific Information
Display Name:
Willow
Route of Exposure:
Inhalation
Family:
Salicaceae
Species:
Salix caprea
Latin Name:
Salix caprea
Other Names:
Willow, Goat willow, Great sallow, Pussy willow
Summary
Willow trees (Salix caprea) are distributed across temperate regions of Europe, North America, western temperate Asia and north-east Africa. Salix pollen is a minor to moderate allergen source causing allergic rhinitis and asthma. Willow pollen shows cross-reactivity with other members of the Salicaceae family (mainly poplars) and with beech.
Allergen
Nature
Willows (Salix caprea) are cool-climate trees found commonly across most of Europe, North America, western temperate Asia and northeast Africa (1). Willow trees flower from February to May, producing pollen on catkins (a slim, cylindrical flower cluster or spike); they are both wind- and insect-pollinated (2). Peak pollen production occurs in April in the UK, with a low to medium emissions strength (3).
Taxonomy
Taxonomic tree of Salix genus (4) |
|
Domain |
Eukaryota |
Kingdom |
Plantae |
Phylum |
Spermatophyta |
Subphylum |
Angioospermae |
Class |
Dicotyledonae |
Family |
Salicaceae |
Genus |
Salix |
Tissue
Tree pollen
Epidemiology
Worldwide distribution
In a review of 36 publications of pollen allergy in the Middle East, an average of 10.9% of the study populations were allergic to willow pollen (5).
Pediatric issues
In a US study of 123 children aged 2-8 years with allergic rhinitis, willow was a significant sensitizing allergen, with the highest prevalence in children ages 2-3 years (6).
Environmental Characteristics
Worldwide distribution
Salicaceae species are fast-growing trees used for timber production, paper, fences, shelter, nets, rope, basket-weaving, as a biomass fuel, for ornamental purposes and to control soil erosion (7). Willow is also widely used in traditional medicine and contains numerous biologically active compounds including salicilin, a pro-drug for salicylic acid (aspirin) (7).
Route of Exposure
Main
The main route of exposure is inhalation.
Detection
Willow pollen is sampled using a volumetric trap such as the Hirst-type pollen trap (8).
Clinical Relevance
Salix pollen is associated with allergic rhinitis and asthma. It has been considered a minor allergen source due to its low airborne pollen counts (3). However, in regions where willow trees are common, airborne pollen loads may be sufficient to cause significant allergen sensitization (2, 6). Salicaceae species were among the ten most allergenic tree pollens described in a review of common tree pollens in the Middle East (5). In a study of 866 allergic Turkish patients, 45.8% showed a positive skin prick test to Salix caprea (9).
Prevention and Therapy
Prevention strategies
Avoidance
Allergenic vegetation maps may contribute to allergy risk assessments by showing the location of willow 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 (3).
Molecular Aspects
Cross-reactivity
Strong cross-reactivity between pollens has been reported, as well as moderate cross-reactivity between Salicaceae and Fagales (beech) (2)
Compiled By
Author: RubyDuke Communications
Reviewer: Dr. Christian Fischer
Last reviewed:January 2022
References
- LOINC. Willow (Salix caprea) 2021 [cited 2021 18.11.21]. Available from: https://loinc.org/LP13974-8/.
- Costache A, Berghi ON, Cergan R, Dumitru M, Neagos A, Popa LG, et al. Respiratory allergies: Salicaceae sensitization (Review). Exp Ther Med. 2021;21(6):609.
- 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.
- CABI. Salix (Willows) Wallingford, UK2021 [cited 2021 18.11.21]. Available from: https://www.cabi.org/isc/datasheet/48455.
- Mansouritorghabeh H, Jabbari-Azad F, Sankian M, Varasteh A, Farid-Hosseini R. The Most Common Allergenic Tree Pollen Grains in the Middle East: A Narrative Review. Iran J Med Sci. 2019;44(2):87-98.
- Wong V, Wilson NW, Peele K, Hogan MB. Early Pollen Sensitization in Children Is Dependent upon Regional Aeroallergen Exposure. J Allergy (Cairo). 2012;2012:583765.
- Tawfeek N, Mahmoud MF, Hamdan DI, Sobeh M, Farrag N, Wink M, et al. Phytochemistry, Pharmacology and Medicinal Uses of Plants of the Genus Salix: An Updated Review. Front Pharmacol. 2021;12:593856.
- Oteros J, Pusch G, Weichenmeier I, Heimann U, Möller R, Röseler S, et al. Automatic and Online Pollen Monitoring. Int Arch Allergy Immunol. 2015;167(3):158-66.
- Yalcin AD, Basaran S, Bisgin A, Polat HH, Gorczynski RM. Pollen aero allergens and the climate in Mediterranean region and allergen sensitivity in allergic rhinoconjunctivitis and allergic asthma patients. Med Sci Monit. 2013;19:102-10.
