Allergen of the Month—Black Wattle

Allergen of the MonthdBlack Wattle There are well over a thousand species of Acacia: shrubs and trees found within the dry tropics of both northern and southern hemispheres, primarily between 40 north and south of the equator, with about half the species found in Australia.1 There are at least six native Acacia species in the United States which are excellent sources of honey.2 Black wattle, A melanoxylon, also known as Australian or Tasmanian blackwood, is a native of New South Wales and Tasmania, and introduced into the Iberian Peninsula, France, and Italy, as well as California.3,4 Acacia wood is hard, heavy, and hot burning, and is used in furniture and carving.2,3 Black wattle is planted for timber, with fine-grained wood used for construction, furniture and musical instrumentmaking.1,3,5 However, it is now considered an invasive weed-tree in the Azores, South Africa, and California.5 A melanoxylon is rapid growing, medium size pyramidal tree of 20e40 m, living for 15e50 years.1,3 Trunk is covered with gray, shaggy bark. Foliage is dense, with both pinnate leaves and phyllodes (flattened, wide, leaf-like stems).1,4 Flowers are creamy-white fragrant globules. Seed pods are brown.1 Pollination is in early spring through to autumn, depending on locale.3,6 Although doubt on importance as pollinosis-inducers is cast on primarily entomophilous plants, Acacia has numerous reports supporting its role in hayfever.6e8 Acacia sensitization was found in 25.6% of Arabian asthmatics, 21.5% of Malaysian asthmatics, and 19% of Thai patients with allergic rhinitis.9e11 Occupational asthma and airborne contact dermatitis have been reported from A melanoxylon wood.12,13 Rowe felt that Acacia pollen was potent enough to induce not only rhinitis and asthma, but dermatitis and “pollen toxemia.”14 Acacia has been incriminated in vernal keratoconjunctivitis.15 Genus Acacia is within subfamily Mimosoideae, family Fabaceae (Leguminosae), which contains acacia, mimosa, and mesquite. Two other subfamilies are Caesalpinioideae, with honey locust and redbud, and Faboideae, with black locust and alfalfa.16 Moderate cross-reactivity between A. farnesiana and mesquite, Prosopis juliflora, has been shown with ELISA inhibition.17 RAST inhibition has been demonstrated between perennial ryegrass, Lolium perenne, and Acacia.18 Acacia grains are compound, polyads with almost always 16 cells, rarely with 32 cells, with a tetrahedral, two-layer core of four cells each. Diameter is 38e54 mm. Exine is tectate, with indistinct columnar and foot layer. Surface is smooth to granular.19,20 Text & Photography: Richard W. Weber, M.D. References [1] Heywood VH. Acacias (genus Acacia). In: Hora B, editor. Oxford Encyclopedia of Trees of the World. New York: Crescent Books; 1986:201e204. [2] Simpson BJ. A Field Guide to Texas Trees. Houston: Gulf Publishing Co; 1999:39e44. [3] Polunin O. Flowers of Europe: A Field Guide. London: Oxford University Press; 1969:175e181. [4] Sibley DA. The Sibley Guide to Trees. New York: Alfred A. Knopf; 2009: 117e119. [5] Acacia melanoxylon. http://en.wikipedia.org/wiki/Acacia_melanoxylon. Accessed October 16, 2014.

[6] Lewis WH, Vinay P, Zenger VE. Airborne and Allergenic Pollen of North America. Baltimore: Johns Hopkins University Press; 1983:45e51. [7] Lewis WH, Vinay P. North American pollinosis due to insect-pollinated plants. Ann Allergy. 1979;42:309e318. [8] Ariano R, Panzani RC, Amedeo J. Pollen allergy to mimosa (Acacia floribunda) in a Mediterranean area: an occupational disease. Ann Allergy. 1991;66:253e256. [9] Bener A, Safa W, Abdulhalik S, Lestringant GG. An analysis of skin test reactions in asthmatics in a hot climate and desert environment. Allerg Immunol (Paris). 2002;34:281e286. [10] Sam C-K, Padmaja K, Liam C-K, et al. A study of pollen prevalence in relation to pollen allergy in Malasian asthmatics. Asian Pac J Allergy Immunol. 1998;16:1e4. [11] Pumhirin P, Towiwat P, Mahakit P. Aeroallergen sensitivity of Thai patients with allergic rhinitis. Asian Pac J Allergy Immunol. 1997;15:183e185. [12] Wood-Baker R, Markos J. Occupational asthma due to blackwood (Acacia melanoxylon). Aust N Z J Med. 1997;27:452e453. [13] Correia O, Barros MA, Mesquita-Guimarães J. Airborne contact dermatitis from the woods Acacia melanoxylon and Entandophragma cylindricum. Contact Derm. 1992;27:343e344. [14] Wodehouse RP. Hayfever Plants. New York: Hafner Publishing Co; 1971: 129e135. [15] Kosrirukvongs P, Vichyanond P, Wongsawad W. Vernal keratoconjunctivitis in Thailand. Asian Pac J Allergy Immunol. 2003;21:25e30. [16] Judd WS, Campbell CS, Kellogg EA, Stevens PF. Plant Systematics: A Phylogenetic Approach. Sunderland, MA: Sinauer Associates; 1999: 282e288. [17] Shamsbiranvand M-H, Khodadadi A, Assarehzadegan M-A, et al. Immunochemical characterization of Acacia pollen allergens and evaluation of cross-reactivity pattern with the common allergenic pollens. J Allergy. 2014:ID409056. [18] Howlett BJ, Hill DJ, Knox RB. Cross-reactivity between Acacia (wattle) and rye grass pllen allergens. Detection of allergens in Acacia (wattle) pollen. Clin Allergy. 1982;12:259e268. [19] Wodehouse RP. Pollen Grains. New York: McGraw-Hill; 1935:432e436. [20] Ye ST, Qiao B, Wang LL, et al. Color Atlas of Air-borne Pollens and Plants in China. Beijing: Peking Union Medical College Press; 2004:154e156:339.

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