Grass Pollens
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Grass pollens Allergy – Which allergens? Authors: Dr Harris Steinman and Dr Sarah Ruden, Allergy Resources International, P O Box 565, Milnerton 7435, South Africa, [email protected] All rights reserved. No part of this publication may be reproduced in any form without the written consent of Phadia AB. ©Phadia AB, 2004, 2007 Design: RAK Design AB, 2004, 2007 Printed by: X-O Graf Tryckeri AB, Uppsala, Sweden ISBN 91-973440-3-6 Contents Introduction ............................................................ 5 g17 Bahia grass .................................................. 9 g201 Barley ........................................................ 11 g2 Bermuda grass ............................................ 13 g11 Brome grass ............................................... 19 g71 Canary grass ............................................... 21 g3 Cocksfoot ................................................... 25 g7 Common reed ............................................. 31 g14 Cultivated oat ............................................. 33 g12 Cultivated rye ............................................. 35 g15 Cultivated wheat ......................................... 39 g204 False oat-grass ............................................ 41 g10 Johnson grass ............................................. 43 g202 Maize, Corn ................................................ 47 g4 Meadow fescue ........................................... 51 g16 Meadow foxtail ........................................... 55 g8 Meadow grass, Kentucky blue ...................... 57 g9 Redtop, Bentgrass ....................................... 63 g5 Rye grass ................................................... 65 g203 Salt grass ................................................... 73 g1 Sweet vernal grass ...................................... 75 g6 Timothy grass ............................................. 79 g13 Velvet grass ................................................ 87 g70 Wild rye grass ............................................. 91 Mixes: gx1 ................................................................. 93 gx2 ................................................................. 93 gx3 ................................................................. 93 gx4 ................................................................. 93 gx6 ................................................................. 93 3 4 Grass Pollen Allergens Familiar features of the grasses, or Poaceae on atmospheric conditions and the type of (also known as Gramineae), include small, pollen, may have consequences even for inconspicuous flowers, linear, sheathing people outside the immediate areas where leaves, and tufts or spikes. The grasses the crops and pastures grow. (Maize pollen constitute a huge family, with around 8,000 is unusually dense and can be expected to species. Grasses are also very widespread, be found in lower concentrations in the probably covering about 20% of the world's atmosphere, but many other crops produce surface. They made a major contribution to pollen that travels far more efficiently). the development of human culture, as they Among the major allergenic offenders were certainly some of the first plants in among grasses are Rye grass, Timothy grass, cultivation, helping in the transition from Bermuda grass and Cocksfoot. But the hunting and gathering to agriculture about epidemiological patterns are of course 10,000 years ago. Triticum (Wheat) and dependent not only on such factors as the Hordeum (Barley) were prominent in the size and weight of the pollen grains, the Middle Eastern Fertile Crescent, the “cradle potency of the allergens and the distribution of civilisation”, from earliest recorded times. of plants, but also on the history of Grasses of far more types than the few whose sensitisation in particular populations seed is edible for humans served as forage – including such diverse influences as cross- and fodder for livestock and as tools for land reactivity and migration. Clinical studies, alteration and reclamation. Property despite much progess, will still have much ownership and trade, and along with them to reveal in the future about grass pollen the state, art, technology and so on, would allergy. probably not have developed without the value grasses added to land. Cross-reactivity Figure 1 is an illustration of one probable Allergen exposure set of relationships of the relevant grasses Today, much of the grass pollen that to each other. Though it is far from humans are exposed to has ornamental or universally agreed on, this schema can be incidental sources: lawns, parks, gardens and useful in beginning a discussion of cross- wasteland. The push for “green space” in reactivity. cities and the spread of suburbs have been Cross-reactivity can be expected to forces working against the distancing of roughly follow botanical relationships, but people from grass exposure, distancing that some unevenness in the patterns should be would otherwise be a result of large-scale noted. Group 4 allergens, for example, may urbanisation. Ironically, some asthmatics be a source of especially strong cross-reactivity who moved to arid regions like Arizona in within the Pooideae subfamily (1-3), but this the United States quickly found their appearance may, on the other hand, be a environment becoming grass-filled again, function of the importance of this subfamily from irrigation-fed proliferation of lawns. in allergy, which perhaps causes it to be more Moreover, the human population's recent intensively studied. Also outstandingly dramatic growth has naturally been notable is the role of Group 1 and Group 5 accompanied by increased demand for allergens, with some of the studies pointing cheap, relatively easily produced food: to the potential for strong cross-reactivity grasses play a starring role in keeping the not only between tribes but sometimes even planet fed. The “green revolution” has between subfamilies (4-9). resulted in higher-yield crops, with more grain produced per hectare; and also in deforestation, as more land has been brought under cultivation and converted into pasturage. All of this has placed more grass pollen in the air, a change which, depending 5 As might be expected, there is potential professionals and patients alike have for cross-reactivity between the pollen of a fatalistically accepted almost constant particular grass and its edible grain, or even discomfort during the “allergy season”. another grain. This has been supported by, (This is approximately May to July in for instance, immunological similarity not temperate climates of the Northern only between Rye pollen and Rye flour, but Hemisphere, and as long as March to also between Rye pollen and Wheat flour (10). November in the north's tropical and sub- tropical climates. In the Southern The existence of panallergens such as Hemisphere the pollen seasons are of course profilin allow for much broader cross- roughly reversed along with the seasons. In reactivity, in this case extending to tree some grass-rich areas of southern Africa, the pollen, weed pollen and plant-derived foods pollen season is 10 months long. A strategy of distantly related species. Among the almost as unsatisfactory as no treatment is pollens, Olive tree, Birch, Mugwort, Wall chronic medication applied in a “shot-gun” pellitory, Plaintain and Ragweed are fashion to deaden a group of symptoms: red, prominent in studies of cross-reactivity with swollen, itchy, and/or watery eyes grass pollen; among foods and other (conjunctivitis), sneezing, congenstion, substances, Apple, Celery, Melon, Carrot, runny nose, and/or nasal itching (rhinitis), Kiwi and Latex are significant in the same and asthma. The classic term “hay fever” connection (11-20). Oral Allergy Syndrome used to cover the syndrome invokes the may be involved (21). picture of a mild and transitory problem, and the popular media have generally Clinical experience depicted grass pollens as causing something Clinically as well as epidemiologically, grass approximating “the sniffles” – a minor pollen allergy is one of the more nebulous personal and social irritation. But the role and frustrating types of allergic disease. grass pollens commonly play in allergic Without routine identification of the specific asthma and their importance in cross- allergens affecting patients, to allow for reactivity show that they should be taken avoidance strategies, many health seriously and individually identified. Family Subfamilies Tribes Genera (species ex.) Paniceae Paspalum (Bahia grass) Panicoideae Andropongoneae Zea (Maize) Sorghum (Johnson grass) Triticeae Elymus (Wild rye grass) Triticum (Cultivated wheat) Hordeum (Barley) Aveneae Holcus (Velvet grass) Pooideae Arrhenatherum (False oat-grass) Anthoxanthum (Sweet vernal grass) Avena (Cultivated oat) Phalaris (Canary grass) Poaceae() Gramineae Agrostideae Phleum (Timothy) Alopecurus (Meadow foxtail) Agrostis (Redtop) Poeae Distichlis (Salt grass) Lolium (Rye grass) Dactylis (Cocksfoot) Poa (Meadow grass) Festuca (Meadow fescue) Hordeae Secale (Cultivated rye) Bromeae Bromus (Brome grass) Arundinoideae Arundineae Phragmites (Common reed) Chloridoideae Chlorideae Cynodon (Bermuda grass) Figure 1. Grasses and their botanical relations, adapted from L Yman (24). 6 ImmunoCAP™ grass allergens available for IgE antibody testing g17 Bahia grass Paspalum notatum g201 Barley Hordeum vulgare Allergen components – Recombinant / g2 Bermuda grass Cynodon dactylon purified native g11 Brome grass Bromus