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Western ragweed is found across most of North America, including northern Mexico. Its range is extensive but its incidence is only significant in the Great Plains and Great Basin in the US. It is also common in Australia and Mauritania.

Western ragweed

Code: w2
Latin name: Ambrosia psilostachya
Source material: Pollen
Family: Asteraceae (Compositae)
Common names: Western ragweed, Perennial ragweed
Allergen Exposure
Geographical distribution
Western ragweed is found across most of North America, including northern Mexico. Its range is extensive but its incidence is only significant in the Great Plains and Great Basin in the US. It is also common in Australia and Mauritania.

Western ragweed is an erect, coarse herbaceous perennial with a creeping rootstock. The leaves are soft, green and opposite or alternate. The leaves are deeply pinnately lobed, hairy, and with irregularly toothed margins. Its foliage is similar to that of False ragweed, but its burs are shaped like those of Giant ragweed. Unlike Ragweed and Giant ragweed, Western ragweed can reproduce vegetatively from creeping roots (rhizomes), which often gives it a straight-line pattern across lawns and waste areas.

Western ragweed flowers from July to November. It is wind-pollinated, releasing millions of pollen grains into the air. However, the presence of the pollen in honey indicates some insect pollination. The plant is monoecious (male and female organs are separate, but occur on the same plant), with the staminate (pollen-producing) heads at the leafless tips of the branches, and the single-flowered pistillate (seed-producing) heads clustered lower down. The fruits are small burs, with the involucre, sometimes slightly spiny or beaked, enclosing the fruit.

Western ragweed is not as large or as abundant as the Ragweed of the more eastern parts of the continent, and is therefore less of an allergy problem.

Western ragweed occurs on plains, dry fields, meadows and prairies, but also along roadsides and in waste places. It spreads rapidly and becomes a pest, especially when it invades cultivated lands and pastures. If dairy cows eat it, their milk becomes bitter.

Unexpected exposure
The leaves of the plant are used in herbal medications. A tea made from the roots is used as a herbal remedy. The pollen is harvested commercially and manufactured into homeopathic preparations for the treatment of allergies to the plant.

The following allergen have been characterised:

Amb p 5 has been characterised (1-3).
Ragweed pollen contains a profilin, though this allergen has not been characterised (4-5).

Potential cross-reactivity
With the use of a serum pool from patients sensitive to Short ragweed, the cross-reactivity of IgE antibodies to six Ragweeds was studied through the radioallergosorbent test. Extracts were analysed for their inhibitory activities, with solid-phase allergens prepared from all of the Ragweed pollens. Also, samples of serum were absorbed with the various solid-phase allergens and the reactivity of the remaining IgE antibodies was determined. Two patterns of reactivity were observed. Short, Giant, Western, and False ragweeds displayed comparable reactivity in both inhibition and absorption experiments. Slender and Southern ragweed were considerably less active, indicating that they lacked allergenic groupings possessed by the other species. These same patterns of cross-reactivity were found using Ragweed pollens from four commercial sources (6).

Further cross-reactivity among the various Ragweeds can be inferred due to the high cross-reactivity among various other members of the genus Ambrosia and of the family Asteraceae. For example, cross-reactivity among Chamomile tea extract, pollen of Matricaria chamomilla, A. vulgaris (Mugwort), and A. trifida (Giant ragweed) was demonstrated by an ELISA-inhibition study (7). Further evidence confirming cross-reactivity among members of the Ragweed genus was obtained in a study using a fluorescent allergosorbent test, in which similar antigenic determinants were found among Short and Giant ragweed, Cocklebur, Lamb's quarters, Rough pigweed, Marshelder, and Goldenrod. Cocklebur and Giant ragweed were highly potent in their ability to competitively bind to Short ragweed IgE. The other pollens demonstrated lower potency of cross-reacting antigens (8). Also, a water-insoluble material, extracted from Short ragweed and False ragweed pollen, contained at least five proteins. Two (RFA2 and RFB2) were isolated and shown to possess antigenicity as well as allergenicity. Immunodiffusion tests of RFB2, isolated from False ragweed and Short ragweed, showed immunological identity (9).

Considering the close cross-reactivity described above, the following further possibilities should be considered.

Mugwort, Ragweed, and Timothy grass pollen share IgE epitopes with Latex glycoprotein allergens. The presence of common epitopes might in part explain clinical symptoms on contact with Latex in patients allergic to pollen. In this study, any previously known panallergen was not detected (10).

An association between Ragweed pollinosis and hypersensitivity to Cucurbitaceae vegetables (e.g., Watermelon, Cantaloupe, Honeydew Melon, Zucchini, and Cucumber) and Banana has been reported. Up to now three allergens have been identified as candidates for causing this cross-reactivity: profilin, Bet v 1, and a 60-69 kDa allergen (11). Further evidence for cross-reactivity between Cucurbitaceae and Ragweed was found in a study that reported that of the sera of 192 allergic patients, 63% contained anti-Ragweed IgE, and among these patients, 28% to 50% had sera containing IgE specific for any single gourd family member. The extracts of Watermelon and Ragweed inhibited each other in a dose-dependent manner (12).

Ragweed profilin can be expected to result in cross-reactivity between this plant and other plants containing profilin. This has been demonstrated between Ragweed and Persimmon (5). In a second study, 35 of 36 patients' sera containing IgE to Ragweed profilin reacted with profilin from Latex, indicating structural homologies between profilin from Latex and Ragweed. Because profilin is also present in Banana extract, it is likely to be involved in cross-sensitivity between Banana and Latex (4).

In addition to profilin, Mugwort and Ragweed pollen contain a number of other cross-reactive allergens, among them the major Mugwort allergen Art v 1. These cross-reactive IgE antibodies could result in clinically significant allergic reactions (13). Evidence of further cross-reactivity between Mugwort and other members of the Asteraceae family (of which Ragweed is a member) consists in the high degree of in vivo cross-reactivity between Matricaria chamomilla (Camomile) and Mugwort (14).

Cross-reactivity between Sunflower and other Asteraceae pollens (Mugwort, Marguerite, Dandelion, Goldenrod, and Short ragweed) has also been demonstrated by RAST and immunoblotting inhibition experiments. Mugwort pollen exhibited the greatest degree of cross-reactivity with Sunflower pollen, whereas at the other end of the spectrum, Short ragweed showed fewer cross-reactive epitopes (15).

Celery cross-reacting with Ragweed has also been reported, but a panallergen was not identified in these studies (16-17).

Binding to IgE from Ginkgo pollen proteins (Ginkgo biloba L.) was shown to be almost completely inhibited by Oak, Ryegrass, Mugwort and Ragweed, but only partially by Japanese Hop and rBet v 2 from Birch tree pollen (18). A panallergen may be indicated but was not isolated.

Sera from subjects allergic to White Cypress Pine, Italian cypress, Ryegrass or Birch pollen were shown to have IgE antibodies that reacted with pollens from these four species and from Cocksfoot, Couch grass, Lamb's quarters, Wall pellitory, Olive, Plantain and Ragweed. The authors concluded that the presence of pollen-reactive IgE antibodies may not necessarily be a true reflection of sensitising pollen species (19).

The Japanese Cypress tree pollen allergen, Cha o 1, has a 46 to 49% similarly to the major allergens of Short ragweed, Amb a 1 and Amb a 2 (20).

A panallergen has been identified in Birch pollen, Ragweed pollen, Timothy grass pollen, Celery, Carrot, Apple, Peanut, Paprika, Anise, Fennel, Coriander and Cumin. EAST inhibition and immunoblot inhibition demonstrated that cross-reactions between Mango fruits, Mugwort pollen, Birch pollen, Celery, and Carrot are based on allergens related to Bet v 1 and Art v 1, the major allergens of Birch and Mugwort pollen, respectively (21).

Pollen of Artemisia annua is considered to be one of the most important allergens in autumnal hay fever in China, just as Ragweed is in North America. Extracts of pollen-free Artemisia annua components were found to contain similar allergens to those of Ragweed pollen. In 52 subjects sensitive to Artemisia pollen, 92.3% were shown on skin prick testing to have IgE antibodies to this allergen, 100% gave positive responses in intradermal tests, 66.7% gave positive responses in intranasal challenges, and 59.3% gave positive responses in bronchial provocation tests (22).

Ragweed pollen appears to also be cross-reactive with pollen from Yellow dock (Rumex crispus). When monoclonal antibodies with different specificity were applied against the major allergenic components of Ragweed pollen, the monoclonal antibodies reacted with antigens of Yellow dock pollen. In a preliminary study, sera of 2 patients containing IgE antibodies to Ragweed pollen antigens also reacted to the 40K component of Yellow dock pollen. In specific IgE tests on 109 patients with bronchial asthma, 22 had a positive reaction to a crude extract of Ragweed pollen, and 18 also reacted to a crude extract of Yellow dock pollen (23).

Ragweed, and in particular Short ragweed (A. artemisiifolia), is clinically the most important source of seasonal aeroallergens, as it is responsible for both the majority of cases and the most severe cases of allergic rhinitis. Ragweed pollen also contributes significantly to exacerbation of asthma and allergic conjunctivitis. Ragweed pollen has also been implicated in eustachian tube dysfunction in patients with allergic rhinitis and contact dermatitis. Copyright Copyright © 2006 Phadia AB. Source: ImmunoCap, ImmunoCap

Ambrosia psilostachya is a species of ragweed known by the common names Cuman ragweed, perennial ragweed, and western ragweed.

It is native to most of North America including all of southern Canada, nearly all of the continental United States, and the northern half of Mexico. It is a common plant in many habitat types, including disturbed areas such as roadsides. It can be found in parts of Eurasia as an introduced species. This is an erect perennial herb growing a slender, branching, straw-colored stem to a maximum height near two meters, but more often remaining under one meter tall. Leaves are up to 12 centimeters long and vary in shape from lance-shaped to nearly oval, and they are divided into many narrow, pointed lobes. The stem and leaves are hairy. The top of the stem is occupied by an inflorescence which is usually a spike. The species is monoecious, and the inflorescence is composed of staminate (male) flower heads with the pistillate heads located below and in the axils of leaves. The pistillate heads yield fruits which are achenes located within oval-shaped greenish-brown burs about half a centimeter long. The burs are hairy and sometimes spiny. The plant reproduces by seed and by sprouting up from a creeping rhizome-like root system. This plant had a number of medicinal uses among several different Native American groups. Copyright Text is available under the Creative Commons Attribution/Share-Alike License. See for details. Source: Wikipedia, Wikipedia

Basic Part Properties

Part Display Name
Western Ragweed (Ambrosia psilostachya)
Part Type
Component (Describes the core component or analyte measured)
Created On
Construct for LOINC Short Name
West Ragweed

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Language Variants Get Info

Tag Language Translation
zh-CN Chinese (China) 多年生豚草
Synonyms: 菊科;西部豚草
fr-CA French (Canada) Ambrosia psilostachya
et-EE Estonian (Estonia) Kare ambroosia
es-ES Spanish (Spain) Ambrosía del oeste (Ambrosia psilostachya)
it-IT Italian (Italy) Ambrosia psilostachya
Synonyms: Ambrosia Occidentale (Ambrosia psilostachya)
tr-TR Turkish (Turkey) Ambrosia psilostachya
ru-RU Russian (Russian Federation) Ambrosia psilostachya
Synonyms: Амброзия голометельчатая (Ambrosia psilostachya)
nl-NL Dutch (Netherlands) zandambrosia
Synonyms: kale ambrosia; Ambrosia psilostachya
fr-BE French (Belgium) Ambrosia psilostachya
Synonyms: Ambroisie,Ambroisie à épis grêles, w2