Firebush (Kochia)

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Code: w17
Latin name: Kochia scoparia (Synonyms: Bassia scoparia, Chenopodium scoparia)
Source material: Pollen
Family: Amaranthaceae (Chenopodiaceae)
Common names: Firebush, Kochia, Common Kochia

Allergen Exposure

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 south-westwards. 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 2m 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 5cm-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 2mm 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.

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.

Allergen Exposure

No allergens from this plant have yet been characterised.

In a study of sera from 20 US donors with a positive clinical history and strong skin prick test to Salp pollen extract (Salsola pestifer/ Russian thistle / saltwort), Koc s contained one major and four minor allergens of which proteins of 35 and 55 kDa were suggested to be important allergens. (1)

In a study of Iranian allergic patients sensitised to Amaranthus retroflexus (Common pigweed) pollen, several allergenic components (85, 45, 39, 18, 15, and 10 kDa) of the A. retroflexus pollen extract were recognised in patients' sera and the IgE reactivity of the pollen extract was partially inhibited by Chenopodium album, K. scoparia, and Salsola kali. Three proteins (39, 45, and 66 kDa) were suggested as the common allergenic components among the pollens. (2)

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. (3, 4)

Clinical Experience

IgE mediated reactions

Anecdotal evidence suggests that asthma, allergic rhinitis and allergic conjunctivitis are common following exposure to pollen from Kochia; however, few specific studies have been reported to date. (5, 6, 7)

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. (5)

In a study in the Midwestern USA, evaluating the frequency of sensitisation to cannabis pollen, found that 61% were skin prick positive for cannabis and all subjects were also skin test positive to weeds pollinating during the same period: Ragweed, Pigweed, Cocklebur, Russian thistle, Marsh elder, and Kochia. (8)

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 2 (nd) and 7 (th) most prevalent allergen sensitising the respective groups.(7)

Kochia pollen is also common in Tehran, Iran, (9) and a common cause of sensitisation in St. Louis, Missouri, USA. (10)

Of 327 adult patients with respiratory, dermatologic and ophthalmologic diseases of suspected allergic origin who attended a Hospital based in the United Arab Emirates, skin prick tests found that 244 patients (74.6%) were sensitised to at least one allergen. The twelve most common allergens were: Mesquite (45.5%), Grass Mix (40.7%), Cottonwood (33.1%), Bermuda grass (31.3%), Kochia (25.8%), Acacia (25.6%), Alfalfa (22.9%), Chenopodium (19.6%), Date palm (13.8%), Cockroach (14.7%), house dust (11.9%) and dust mite (9.5%). (6)

Compiled by Dr Harris Steinman,


  1. Wurtzen PA, Nelson HS, Lowenstein H, Ipsen H. Characterization of Chenopodiales (Amaranthus retroflexus, Chenopodium album, Kochia scoparia, Salsola pestifer) pollen allergens. Allergy 1995;50(6):489-97.
  2. Tehrani M, Sankian M, Assarehzadegan MA, Falak R, Jabbari F, Varasteh A. Immunochemical characterization of amaranthus retroflexus pollen extract: extensive cross-reactive allergenic components among the four species of amaranthaceae/chenopodiaceae. Iran J Allergy Asthma Immunol 2010;9(2):87-95.
  3. Lombardero M, Duffort O, Selles JG, Hernandez J, Carreira J. Cross-reactivity among Chenopodiaceae and Amaranthaceae. Ann Allergy 1985;54(5):430-6.
  4. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
  5. Pumhirun P, Towiwat P, Mahakit P. Aeroallergen sensitivity of Thai patients with allergic rhinitis. Asian Pac J Allergy Immunol 1997;15(4):183-5.
  6. Bener A, Safa W, Abdulhalik S, Lestringant GG. An analysis of skin prick test reactions in asthmatics in a hot climate and desert environment. Allerg Immunol (Paris) 2002;34(8):281-6.
  7. 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.
  8. Stokes JR, Hartel R, Ford LB, Casale TB. Cannabis (hemp) positive skin tests and respiratory symptoms. Ann Allergy Asthma Immunol 2000;85(3):238-40.
  9. Shafiee A. Atmospheric pollen counts in Tehran, Iran, 1974. Pahlavi Med J 1976;7(3):344-51.
  10. Lewis WH, Imber WE. Allergy epidemiology in the St. Louis, Missouri, area. IV. weeds. Ann Allergy 1975;35(3):180-7.


As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.