t37 Bald cypress

Allergens within Tree Pollens

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  • Latin name: Taxodium distichum
  • Common names: Bald cypress, Swamp Cypress
  • Source material: Pollen
Family: Some researchers claim that Bald cypress belongs to the family Cupressaceae (1-2), while others place it in a separate family, Taxodiaceae. A third opinion is that these are a single family. 

Allergen Exposure

Geographical distribution
Bald cypress is a deciduous conifer, growing in very wet, swampy, often submerged soils. It is native to humid climates where precipitation ranges from about 760 mm to 1630 mm. It is found from Delaware to south Florida, into Texas and Oklahoma, and north to Indiana. Planted as an ornamental in Europe, it is hardy into southern Canada (3-5). Ancient Bald cypress forests, with some trees more than 1,200 years old, once dominated swamps in the southeastern US (6). Existing trees can be around 500 years of age, and some exceed 40 m in height. Some consider pond cypress (T. ascendens and T. mucronatum) to comprise varieties of T. distichum (3,7-8).

Bald cypress is a large tree, usually reaching over 25 m in height, with a trunk diameter of 2-3 m, and a wide, buttressed, tapering trunk. The bark is light-brown, gray-brown or red-brown, shallowly vertically fissured and scaly, with a stringy texture. The trunk base is deeply ridged. The branches are upright and spreading. Buds are small and inconspicuous. Twigs near the end of the shoots persist, while those on the lower part of the stem are deciduous and fall with the leaves. The leaves are borne on deciduous branchlets that are spirally arranged on the stem but twisted at the base to lie in 2 horizontal ranks, 1-2 cm long and 1-2 mm broad (6). The deciduous needles are 10-19 mm long, soft, flat, and flexible. Leaflets are linear with entire margins. Foliage is soft and light-green with a feathery or plume-like appearance.

The roots send up short, tapering trunks, protruding out of the water or (less often) the ground and known as “cypress knees”.

Bald cypress is unusual in that it is a deciduous conifer, shedding its foliage during the winter months; hence the name “bald”.

The flowers are monoecious. Male and female strobili mature in about 12 months; they are produced from buds formed in the late fall, with pollination in early winter. Male catkins are at least 5 cm long and quite conspicuous during the winter months, arranged in narrow drooping clusters of 10 cm. The seed cones are green, maturing to gray-brown, globular and 2-3.5 cm in diameter. They have from 20 to 30 spirally arranged 4-sided scales, each bearing 1 or 2 (rarely 3) triangular seeds. The number of seeds per cone ranges from 20 to 40. The cones disintegrate when mature to release the large seeds. The seeds are 5 to 10 mm long and are produced every year, but with heavy crops every 3 to 5 years (4).

In Tampa, Florida, in the USA, Oak, Pine, Australian pine, Bald cypress, Cedar, Bayberry and Mulberry contribute to the major tree pollen season, extending from December to May (9).

Environment
Bald cypress heartwood is very resistant to rot (and called “wood eternal”). It is prized for the construction of docks, warehouses, and bridges, as well as interior trim (4). Taxol, an anticancer drug first isolated from the bark of the yew tree (Taxus brevifolia), is also produced in Bald cypress by an endophytic fungus (Pestalotiopsis microspora). Bald cypress is also planted as an ornamental tree.

Allergens
No allergens have been characterised.

Potential cross-reactivity

Potential cross-reactivity for this tree has not been elucidated to date.

Clinical Experience

IgE-mediated reactions
Anecdotal evidence suggests that asthma and hayfever are possible following exposure to pollen from this tree; however, few specific studies on this have been reported to date (10).

Nasal and bronchial Bald cypress challenges verify this tree’s ability to cause both allergic rhinitis and asthma. (10) In a study in which 57 nasal and bronchial provocation tests were performed with Bald cypress pollen extract on 41 subjects, a positive nasal response was elicited in 12 of 17 (71%) subjects with allergic rhinitis and positive Bald cypress pollen skin tests. A positive bronchial challenge was elicited in 2 of 10 asthmatics with positive Bald cypress pollen skin tests. Bald cypress-specific IgE was demonstrated in 7 of the 12 (59%) subjects with a positive nasal challenge, and in 1 of the 2 subjects with a positive bronchial challenge (10).

Compiled by Dr Harris Steinman, harris@zingsolutions.com.

References:

    1. Judd WS, Campbell CS, Kellogg EA, Stevens PF. Plant Systematics: A Phylogenetic Approach. Sunderland, MA, Sinauer Associates, 1999:152-8
    2. Gadek PA, Alpers DL, Heslewood MM, Quinn CJ. Relationships within Cupressaceae sensu lato: A combined morphological and molecular approach.
      Am J Botany 2000;87:1044 -57
    3. Wodehouse RP. Pollen Grains. New York, McGraw-Hill, 1935:268-9
    4. Weber RW. Bald cypress.
      Ann Allergy Asthma Immunol 2006;96(2):A6
    5. Lewis WH, Vinay P, Zenger VE. Airborne and Allergenic Pollen of North America. Baltimore, Johns Hopkins University Press, 1983:11-12,182
    6. Wikipedia contributors, ”Taxodium distichum”, Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Taxodium_distichum&oldid=224763869 (accessed July 10, 2008)
    7. Little EL. The Audubon Society Field Guide to North American Trees: Eastern Region. New York, Alfred A. Knopf, 1980:302-4
    8. Brown CL, Kirkman LK. Trees of Georgia and Adjacent States. Portland, Oregon, Timber Press, 1990:55-7
    9. Bucholtz GA, Lockey RF, Wunderlin RP, Binford LR, Stablein JJ, et al. A three-year aerobiologic pollen survey of the Tampa Bay area, Florida.
      Ann Allergy 1991;67(5):534-40
    10. Bucholtz GA, Lockey RF, Serbousek D. Bald cypress tree (Taxodium distichum) pollen, an allergen.
      Ann Allergy 1985;55(6):805-10

2008



Further Reading