Allergen of the Month—Western Dock

Allergen of the MonthdWestern Dock The genus Rumex contains around 200 species of temperate climate weeds widely distributed throughout the northern hemisphere.1 About two dozen species are found in North America: evenly divided between native and introduced.2 Western dock, Rumex occidentalis (synonym R. aquaticus) is native to North America but is also found throughout Europe. It is found throughout most of Canada, and the western and northeastern United States. R. occidentalis prefers moist to wet meadows, stream-banks, shorelines, tide-flats and beaches, in elevations up to 3000 m.2e6 The leaves of docks are generally edible, though bitter due to tannins and oxalates. When grazed on in excess, docks may result in livestock loss, although poisoning has not been reported with humans.7 Dock roots have been used by Chippewa Indians in poultices for itching and skin eruptions.8 Several Rumex extracts show cancer inhibitory activity.9 Western dock is an erect perennial with a stout taproot and single red-tinted stem that is un-branched below the inflorescence, and 0.5-2 m tall.5,10 Basal leaves are numerous, leathery, heart- to lance-shaped with curly edges. Flowers are pink or green in dense clusters. Rumex species are all wind-pollinated, producing abundant airborne pollen, which may approach that seen with grasses.2,11 Sheep sorrel, R. acetosella, may produce 30,00 grains in one stamen, 180,000 in one flower, and 400 million grains from a single plant.12 Anthesis is most intense from late April through May, persisting into the summer in the U.S., and slightly later in midEurope.2,13 In California and southern Florida, Rumex species may pollinate all year long.2 The impact of Rumex species in causing allergic rhinitis is probably greater than appreciated, but its importance is underestimated because of overlap with the grass pollination season.2 Solomon found numerous symptomatic patients who responded to Rumex skin tests and nasal challenges.14 Polygonaceae is monophyletic, and within the superorder Caryophyllanae, containing Polygonales and Caryophyllales.1 This taxonomy would suggest some reactivity between Rumex species and Chenopod-Amaranth weeds of the family Amaranthaceae. This is undetermined, and cross-reactivity data is limited to preliminary data on Rumex acetosella.14,15 No Rumex allergens have been characterized. Rumex pollen grains are spheroid, 22-34 mm in diameter. The grains are tetracolporate or stephanocolporate, with long, thin, intruding furrows of varying lengths, with a small, ellipsoid pore (1-3x3-6 mm) in the center. The pores are more apparent with grains fixed in glycerine jelly.16 The walls are tectate, with densely spaced columellae, about 1.5 mm thick. Surface is reticulate with thick muri and small luminae. The cytoplasm is densely packed with starch granules.16,17 Text and Photography: Richard W. Weber, M.D. References [1] Judd WS, Campbell CS, Kellogg EA, Stevens PF. Plant Systematics: A Phylogenetic Approach. Sunderland, MA: Sinauer Associates; 1999: pp 252e256. [2] Lewis WH, Vinay P, Zenger VE. Airborne and Allergenic Pollen of North America. Baltimore: Johns Hopkins University Press; 1983: pp 167e171,234. [3] Kershaw L, MacKinnon A, Pojar J. Plants of the Rocky Mountains. Edmonton, AB, Canada: Lone Pine Publishing; 1998: pp 260. [4] Ells J. Rocky Mountain Flora. Golden, CO: Colorado Mountain Club Press; 2006: pp 214. [5] Pojar J, MacKinnon A. Plants of the Pacific Northwest Coast. Edmonton, AB, Canada: Lone Pine Publishing; 1994: pp 130. [6] Polunin O. Flowers of Europe: A Field Guide. London: Oxford University Press; 1969: pp 65e68.

[7] Harrington HD. Edible Native Plants of the Rocky Mountains. Albuquerque: University of New Mexico Press; 1967: pp 90e92. [8] Densmore F. How Indians Use Wild Plants for Food, Medicine & Crafts. New York: Dover Publications; 1974: pp 350e351. [9] Lajter I, Zupkó I, Molnár J, et al. Antiproliferative activity of polygonaceae species from the Carpathian Basin against human cancer cell lines. Phytother Res. 2013;27:77e85. [10] Turner M, Gustafson P. Wildflowers of the Pacific Northwest. Portland, OR: Timber Press Inc; 2006: pp 319. [11] Wodehouse RP. Hayfever Plants. 2nd Ed. New York: Hafner; 1971: pp 107e111. [12] Ogden EC, Raynor GS, Hayes JV, Lewis DM, Haines JH. Manual for Sampling Airborne Pollen. New York: Hafner Press; 1974: pp 22e23. [13] Weryszko-Chmielewska E, Piotrowska K. Airborne pollen calendar of Lublin, Poland. Ann Agric Environ Med. 2004;11:91e97. [14] Solomon WR. An appraisal of Rumex pollen as an aeroallergen. J Allergy. 1969;44:25e36. [15] Weber RW. Cross-reactivity of plant and animal allergens. Clin Rev Allergy Immunol. 2001;21:153e202. [16] Wodehouse RP. Pollen Grains. New York: McGraw-Hill Book Co.; 1936: pp 397e400. [17] Bassett IJ, Crompton CW, Parmalee JA. An atlas of airborne pollen grains and common fungus spores of Canada. Hull, Quebec: Printing and Publishing, Supply and Services Canada; 1978: pp 233e238.

Reprints: Richard W. Weber, M.D. National Jewish Health 1400 Jackson Street Room J326 Denver, CO 80206