t212 Cedar

Allergens within Tree Pollens

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  • Latin name: Libocedrus decurrens
  • Family: Cupressaceae
  • Common names: Cedar tree, Incense-Cedar; White Cedar (Not to be confused with the Cedar trees of the genus Cedrus.)
  • Source material: Pollen
Synonyms: Calocedrus decurrens
 
A tree species producing pollen, which may induce hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
The Incense-Cedar tree is native to the western USA: western Oregon, Nevada, California. It also occurs in Mexico and in western and central Europe. The Incense-Cedar is cultivated worldwide as an ornamental tree.
 
The Incense-Cedar is a resinous, aromatic tree 18 - 45 m tall. The tree has an irregularly angled trunk with a columnar crown. The bark is light- or reddish-brown and deeply and irregularly furrowed into ridges. The leaves are evergreen, shiny, and aromatic when crushed.
 
Incense-Cedar is monoecious: both male and female flowers may be borne on the same tree. The flowers are 6mm, yellow-green strobili, borne on the end of twigs from early September. The pollen is shed from late winter to early spring.
 
The seed cones are inconspicuous in spring, becoming pendent and red-brown to golden-brown in colour when they mature in late summer. Seed dispersal begins in late August and lasts through October. Seeds of Incense-Cedar are carried great distances by wind.
 
Although the large "Cedars" (actually, species of Calocedrus, Chamaecyparis, Cupressus, and Thuja) of western North America tend to look alike at first, the Incense-Cedar is distinguished by its foliage, which is held in flattened vertical sprays.
 
Environment
Incense-Cedar heartwood is ideal for exterior use where moisture is present, and may be found as mud sills, window sashes, sheathing under stucco or brick veneer construction, greenhouse benches, fencing, poles, and trellises. Incense-Cedar is also used in the manufacture of pencils.

Potential Cross-Reactivity

Cross-reactions with other members of this family are possible (1). A high degree of cross-reactivity also occurs among the Cupressaceae and Taxodiaceae families (2).

Clinical Experience

IgE mediated reactions
Incense-Cedar tree pollen can induce asthma, allergic rhinitis and allergic conjunctivitis.
 
Other reactions
Cases of dermatitis from Cedar wood pencils have been described (3);  reactions may be due to the presence of thymoquinone, thymoquinol and carvacrol in the wood (4).

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09  
    2. Alisi C, Afferni C, Iacovacci P, Barletta B, Tinghino R, et al. Rapid isolation, characterization, and glycan analysis of Cup a 1, the major allergen of Arizona cypress (Cupressus arizonica) pollen. Allergy 2001 Oct;56(10):978-84  
    3. Calnan CD. Dermatitis from cedar wood pencils. Transactions and Annual Report of the St John's Hospital Dermatological Society 1972;58: 43  
    4. Zavarin E, Anderson AB. Extractive components from incense-cedar heartwood (Libocedrus decurrens Torrey). I. Occurrence of carvacrol, hydrothymoquinone, and thymoquinone. Journal of Organic Chemistry 1955;20: 82-88

2002



Further Reading