Bald cypress

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Code: t37
Latin name: Taxodium distichum
Source material: Pollen
Family: Taxodiaceae
Common names: Bald cypress, Swamp Cypress

Note regarding Family: Some researchers claim that bald cypress belongs to the family Cupressaceae (Cupressus disticha), (1, 2) while others place it in a separate family, Taxodiaceae. A third opinion is that these are a single family.

Allergen Exposure

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 1 630 mm. In the US 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, 4, 5) Ancient bald cypress forests, with some trees more than 1 200 years old, once dominated swamps in the south-eastern 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, grey-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 grey-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 to10 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)

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 for interior trim. (4) Taxol, an anti-cancer 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.

Allergen Description

Although bald cypress appears to contain a number of allergens, (10) to date only one allergen has been characterised.

The following allergen has been characterised:

  • Tax d 2, a polygalacturonase. (11)

Potential Cross-Reactivity

The cypress family, Cupressaceae, is the most allergenic family in the order Coniferales. This family, which includes the sub-family Taxodioideae, contains cypress (Cupressus and Chamaecypris spp), cedar and juniper (Juniperus spp), bald cypress (Taxodium distichum), redwood and sequoia (Sequoia spp), and Japanese red cedar (Cryptomeria japonica). Members are strongly cross-reactive, with animal antisera and human IgE antibody studies demonstrating consistent cross-inhibition. (12) Older literature has demonstrated the interchangeability of Cupressaceae member crude extracts. (13) Strong homology has been demonstrated between the major (group 1) allergens of the various species. Although amino acid sequences are highly homologous among group 1 allergens, glycosylation sites may differ. (10, 14 )Similarly, a study suggests that conserved homologs of the allergen Cry j 2 of the Japanese cedar tree confer cross-allergenicity among Taxodiaceae and Cupressaceae. (15)

A study evaluated the residual serum samples of adult and paediatric patients with at least 1 positive allergen-specific IgE to a tree pollen (n = 102); testing with commercial reagents found 57 of 102 samples (56%) had bald cypress IgE of 0.1 kUa/L or higher, and 64 of 102 (63%) had red cedar IgE concentrations of 0.1 kUa/L or higher. All samples positive for bald cypress were also positive for red cedar. However, 7 patients (7%) had positive results for red cedar, with values ranging from 0.11 to 0.67 kUa/L, but were negative for bald cypress IgE (<0.10 kUa/L). Inhibition assays revealed that both the red cedar and bald cypress extracts readily inhibited the binding of IgE to the other allergen in a dose-dependent manner. The very similar and strong inhibitions by both bald cypress and red cedar suggest similar antigenic composition, but the 7 serum samples positive for red cedar and negative for bald cypress demonstrate at least one minor antigenic difference. The authors concluded that the results suggest that red cedar extract contains most of the allergens of bald cypress extract, and that testing for red cedar sensitivity will detect nearly all individuals who are sensitive to bald cypress. (10)

Clinical Experience

IgE-mediated reactions

Anecdotal evidence suggests that asthma and hay fever are possible following exposure to pollen from this tree; however, few specific studies on this have been reported to date. (16)

Nasal and bronchial bald cypress challenges verify this tree’s ability to cause both allergic rhinitis and asthma. (13) 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. (13)

Both bald cypress and Japanese red cedar belong to the Taxodioideae family, and authors have suggested that bald cypress extract for immunotherapy will provide protection against both allergens. (17, 18)

Compiled by Dr Harris Steinman, 


  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, Accessed 9 January 2013.
  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. Cannington EM, Roe KL, Young PF, Ownby DR. Sensitization to bald cypress and cross-reactivity with red cedar in Northeastern Georgia. Ann Allergy Asthma Immunol 2012;109(3):220-1.
  11. Fujimoto A, Kado T, Yoshimaru H, Tsumura Y, Tachida H. DNA variation in a conifer, Cryptomeria japonica. EMBL/GenBank/DDBJ databases. 2005; April. Accessed 9 January 2013.
  12. Weber RW. Cross-reactivity of pollen allergens: impact on allergen immunotherapy. Ann Allergy Asthma Immunol 2007;99(3):203-11.
  13. Weber RW. Cross-reactivity of plant and animal allergens. Clin Rev Allergy Immunol 2001;21(2-3):153-202.
  14. Midoro-Horiuti T, Goldblum RM, Kurosky A, Wood TG, Schein CH, Brooks EG. Molecular cloning of the mountain cedar (Juniperus ashei) pollen major allergen, Jun a 1. J Allergy Clin Immunol 1999;104(3 Pt 1):613-7.
  15. Futamura N, Kusunoki Y, Mukai Y, Shinohara K. Characterization of genes for a pollen allergen, Cry j 2, of Cryptomeria japonica. Int Arch Allergy Immunol 2006;143(1):59-68.
  16. Bucholtz GA, Lockey RF, Serbousek D. Bald cypress tree (Taxodium distichum) pollen, an allergen. Ann Allergy 1985;55(6):805-10.
  17. Phillips JF, Jelks ML, Lockey RF. Important Florida botanical aeroallergens. Allergy Asthma Proc 2010;31(4):337-40.
  18. Weber RW. Cross-reactivity of pollen allergens: recommendations for immunotherapy vaccines. Curr Opin Allergy Clin Immunol 2005;5(6):563-9.


As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.