t14 Cottonwood

Allergens within Tree Pollens

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  • Latin name: Populus deltoides
  • Family: Salicaceae
  • Common names: Cottonwood, Poplar tree
  • Source material: Pollen
The botanical family Willow (Salicaceae) consists of Populus and Salix, the latter being true Willows. Populus deltoides is the common designation for Populus species of trees in this genus, but in fact, Populus can be divided into 3 distinct groups: Aspens, Cottonwoods and Poplars.
  • Cottonwood (Populus deltoides)
  • Black Poplar (Populus nigra)
  • Lombardy Poplar (Populus nigra cultivar italica)
  • White Poplar (Populus alba)
  • Aspen (Populus tremula)
A tree species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Cottonwood is a deciduous tree that grows up to 45 m high, and is the fastest-growing native tree in North America In open areas, it typically has a large trunk that divides into upright branches near its base and ascends to form a wide, open, broad, spreading crown. In plantations it tends to have a tall, straight, and relatively branch-free bole with a small rounded crown. On good sites, 35-year-old trees may average 40 m in height, while trees 55 to 65 years old may 53-58 m in height. The root system is quite expansive and can extend over 200 feet from the trunk.
 
Cottonwood is native to eastern North America. The genus Populus contains about 30 species in North America, Europe, North Africa and temperate Asia. It does not occur in the southern hemisphere.
 
Cottonwood is dioecious (having separate sexes); that is, each tree is either male or female, not both. Cottonwood flowers in early spring, with time of pollen production, depending on region. Populus species are entirely wind-pollinated, as distinct from Willows, which are primarily insect-pollinated. The cotton is produced in enormous quantities virtually every year, and can be windblown miles from its origin. This cotton is dispersed only by female trees, and for only about two weeks of the year. Though both sexes flower, only the female tree produces fruit. This is the cottony-coated seed from which the tree gets its name.
 
Environment
Because of its extensive root system, it plays a major role in soil erosion control along the rivers, streams, and lakes.
 
Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

Extensive cross-reactivity could be expected between the species in the genus Populus as well as the species of the genus Salix such as Willow (1). In a study of the cross-reactivity between Cottonwood and Willow, a fairly high degree of relation was indicated, while Cottonwood and Birch showed no relation (2-4).

Clinical Experience

IgE mediated reactions
Pollen from the Cottonwood tree results in asthma, hayfever and allergic conjunctivitis (5). 
 
Allergy to Cottonwood pollen has been shown to be one of the ten most important aeroallergies resulting in clinical symptoms in an Eastern Province of Saudi Arabia, where 38% of 1,159 patients were skin prick test-positive to Cottonwood pollen(6);  and similarly in 614 respiratory allergic patients in Turkey (7). A Hungarian study found that 6.8% of hay fever patients were sensitized to Cottonwood tree pollen; thus in this group of patients, Cottonwood was not an important cause of hay fever (8); and similarly in an early 1975 study in St. Louis, Missouri, USA (9).
 
Cottonwood pollen has been demonstrated to be a major aeroallergen during the pollen season in Tehran, where the tree pollen season extended from the first week of February through the middle of October(10);  as well as in Fairbanks, Alaska (11). In other areas Cottonwood pollen may not be a large component of the total aeroallergen measurement. In Madrid, Spain, the highest airborne presence (from 1979 to 1993) was for Quercus spp. (17%); followed by Platanus spp. (15%), Poaceae spp. (15%), Cupressaceae spp. (11%), Olea spp. (9%), Pinus spp. (7%), Populus spp. (4%), and Plantago spp. (4%). The most predominant pollens from January to April were tree pollens (Cupressaceae, Alnus, Fraxinus, Ulmus, Populus, Platanus, and Morus) (12).
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. Pharmacia Diagnostics AB. Uppsala. Sweden. 1978: ISBN 91-7260-511-1   
    2. Kadocsa E, Bittera I, Juhasz M. Aeropollinologic and allergologic studies for the clarification of "Poplar tree hay fever" [Hungarian] Orv Hetil 1993;134(38):2081-3   
    3. Weber RW. Cross-reactivity among tree pollens: skin test correlations. Ann Allergy 1983;50:363   
    4. Segal AT, Kemp JP, Frick OL. An immunologic study of tree pollen antigens. J Allergy 1970;45:44   
    5. Storms WW. Hay fever symptoms from the cotton of the Cottonwood tree. Ann Allergy 1984;53(3):223-225   
    6. Suliaman FA, Holmes WF, Kwick S, Khouri F, Ratard R. Pattern of immediate type hypersensitivity reactions in the Eastern Province, Saudi Arabia. Ann Allergy Asthma Immunol 1997;78(4):415-8   
    7. Guneser S, Atici A, Cengizler I, Alparslan N. Inhalant allergens: as a cause of respiratory allergy in east Mediterranean area, Turkey. Allergol Immunopathol (Madr) 1996;24(3):116-9   
    8. Kadocsa E, Bittera I, Juhasz M. Aeropollinologic and allergologic studies for the clarification of "Poplar tree hay fever". [Hungarian] Orv Hetil 1993 19;134(38):2081-3   
    9. Lewis WH, Imber WE. Allergy epidemiology in the St. Louis, Missouri, area. III. Trees. Ann Allergy 1975;35(2):113-9   
    10. Shafiee A. Atmospheric pollen counts in Tehran, Iran, 1974. Pahlavi Med J 1976;7(3):344-51   
    11. Anderson JH. A survey of allergenic airborne pollen and spores in the Fairbanks area, Alaska. Ann Allergy 1984;52(1):26-31   
    12. 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

2002



Further Reading