w17 Firebush (Kochia)
Allergens within Weed Pollens
- Latin name: Kochia scoparia
- Family: Chenopodiaceae
- Common names: Firebush, Kochia, Common Kochia,
- Source material: Pollen
A weed species producing copious pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.
Allergen Exposure
Geographical distribution
Kochia is native to southern and eastern Russia, Europe and Asia. It is now naturalised across the northern half of the United States and spreading southwestwards. It is found in many other areas of the world. Kochia is a major source of pollen.
Kochia is an erect annual with many-branched stems. The branching is usually from the base. The branches are 1 to 2 m long, and the bush grows from 50 to 150cm in height. The main stem is often tinged with red. The plant has a deep taproot, up to 5m. The 2- to 5 cm-long narrow leaves are stalkless, pubescent to nearly glabrous, lance-like in shape with hairy margins, and often turning red to purple in autumn. Seedlings emerge in spring and have thick leaves, dull-green above and with magenta undersides.
Kochia flowers in midsummer. The inconspicuous green flowers lack petals and are borne in clusters at the ends of branches and bases of leaves, and each flower is surrounded by a cluster of long hairs. Kochia may be called "Burning Bush" for its reddish-purple colour. Kochia usually flowers in late summer but there is great variation in the flowering time of different populations. The brown flattened seeds are approximately 1 to 2 mm long and grooved on each side. Like many other species of the Chenopodiaceae, Kochia becomes a tumbleweed when mature.
Kochia is difficult to differentiate from Fivehook Bassia. But unlike Kochia, which is usually branched from the base, Fivehook Bassia's branching is along the main stem.
Environment
Kochia is a highly aggressive and damaging weed, affecting crop production in many parts of the world, particularly cereal production. Kochia is highly adaptable. It is very drought-tolerant and is commonly found on saline soils, deserts, and coasts. It is found on pasture, rangeland, roadsides, ditch banks, wastelands, and cultivated fields. Kochia is often cultivated as a bedding plant or as an ornamental hedge.
Allergens
No allergens from this plant have yet been characterised.
Potential Cross-Reactivity
An extensive cross-reactivity among the different individual species of the genus could be expected, as well as to a certain degree among members of the families Chenopodiaceae and Amaranthaceae (1-2). Clinical Experience
IgE mediated reactions
Kochia pollen is a common aeroallergen inducing asthma, allergic rhinitis and allergic conjunctivitis (3).
In one study in Thailand, Kochia was shown to be the second most important weed aeroallergen, with 14% of 100 patients with allergic rhinitis sensitised to it (3).
Among 1,159 patients attending an allergy clinic in Saudi Arabia, 51% of Saudi Arab patients and 28% of North American expatriates living in the area were sensitised to Kochia. This weed's pollen was the 2nd and 7th most prevalent allergen sensitising the respective groups (4).
Kochia pollen is also common in Tehran, Iran (5), and a common cause of sensitisation in St. Louis, Missouri, USA (6).
References:
- Lombardero M, Duffort O, Selles JG, Hernandez J, Carreira J. Cross-reactivity among Chenopodiaceae and Amaranthaceae. Ann Allergy 1985;54(5):430-6
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
- Pumhirun P, Towiwat P, Mahakit P. Aeroallergen sensitivity of Thai patients with allergic rhinitis. Asian Pac J Allergy Immunol 1997;15(4):183-5
- Suliaman FA, Holmes WF, Kwick S, Khouri F, Ratard R. Pattern of immediate type hypersensitivity reactions in the Eastern Province, Saudi Arabia. Ann Allergy Asthma Immunol 1997;78(4):415-8
- Shafiee A. Atmospheric pollen counts in Tehran, Iran, 1974. Pahlavi Med J 1976;7(3):344-51
- Lewis WH, Imber WE. Allergy epidemiology in the St. Louis, Missouri, area. IV. weeds. Ann Allergy 1975;35(3):180-7
2002