Rough marshelder
Summary
Rough marshelder (Iva annua) is a coarse-textured plant that grows to a height of around 1-4 feet. This plant is abundantly found in lakes, river bottoms, valleys, lowlands, and damp areas. This weed pollen is predominantly found in the US and extends to Mexico. Rough marshelder pollen can trigger allergic conditions like asthma, allergic rhino-conjunctivitis, and allergic rhinitis. No allergenic proteins from rough marshelder pollen have been identified in the IUIS database. Rough marshelder pollen exhibits cross-reactivity with pollen from short ragweed and ragweed.
Epidemiology
Worldwide distribution
A study confirmed [through skin prick test (SPT) and/or serum specific-IgE] marshelder to be one of the seasonal weed pollen allergens found in the southeast regions of the United States (US).
In a US-based retrospective study, 43.6% (24/55) of patients demonstrated positive SPT towards rough marshelder pollen (allergen).
A Saudi-Arabian based study was conducted on 1159 patients (>5years; with respiratory allergy, allergic rhinitis, and/or bronchial asthma) either from Saudi Arabians or from different nationalities such as western immigrants (majorly North Americans), Indians, Pakistanis, Filipinos, and other Arabian countries. Marshelder pollen has been revealed to be one of the contributors for frequent pollen-mediated allergic reactions among 23.4% (271/1159) of the patients.
Route Of Exposure
Main
The route of exposure for rough marshelder pollen is through inhalation (airway).
Clinical Relevance
As per studies, exposure to weed (like marshelder) pollen may induce allergic conditions such as allergic rhinitis, allergic rhino-conjunctivitis, and asthma.
Allergic rhinitis (AR) and allergic rhino-conjunctivitis (ARC)
A retrospective analysis conducted on 1137 rhinitis patients (4-79 years) reported marshelder/poverty as one of the most sensitizing weed allergens with a prevalence rate of 27.8% among patients.
A Saudi Arabia-based study was conducted on 1159 patients (>5years) with allergic rhinitis, respiratory allergic, and/or bronchial asthma. Marshelder pollen has been reported as one of the pollens responsible for frequent allergic reactions in 23.4% (271/1159) of patients in the study population.
A study was conducted on 30 randomly selected patients (with allergic rhino-conjunctivitis and/or asthma) from a total of 78 patients with positive skin prick test (SPT) towards Cannabis. 96% (29/30) of the patients have been observed to possesses positive SPT towards marshelder pollens.
Prevention And Therapy
Prevention strategies
Avoidance
Avoiding exposure to a particular allergen is the initial step towards allergic rhinitis management.
One of the main measures to reduce the symptoms is to cut down the pollen amounts in the respiratory system. During pollen season, allergic patients are suggested to stay indoors or wear a mask outdoors to keep away from pollen allergens. In worsening conditions, patients may be recommended to move or live in a non-pollen area
Cross-Reactivity
Marshelder has been reported to be cross-reactive with ragweed and short ragweed pollen.
References
- Yarnell AR. Iva annua var. macrocarpa: Extinct American Cultigen? American Anthropologist. 1972;74(3):335-41.
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- USDA. USDA Natural Resources Conservation Service 2021 [18-Jan-2021]. Available from: https://plants.sc.egov.usda.gov/core/profile?symbol=IVANA.
- WHO/IUIS. International Union of Immunological Societies Allergen Nomenclature 2021 [21-Jan-2021]. Available from: http://www.allergen.org/search.php?allergensource=roughmarshelder&searchsource=Search.
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