Latin name: Rumex acetosella
Source material: Pollen
Common names: Sheep Sorrel, Field Sorrel, Red Sorrel, Common Sheep Sorrel
See also: Yellow dock w23 (R. crispus)
Sheep sorrel is a perennial herb/weed that originated in Europe and Asia and has become naturalised throughout temperate North America and all other temperate regions across the world. Although grown as an herb, it is also classified as a noxious and invasive weed.
Sheep sorrel is a rhizomatous herb/weed that sometimes forms dense colonies by adventitious shoots from widely spreading roots and rhizomes. Stems are erect, slender, and 10 to 60cm tall. The arrowhead-like mid-green to dark-green fleshy leaves are 2 to 10cm long and 1 to 2cm wide and are situated mostly at the stem base. The leaves are spicy and pungent to the taste and often turn red in autumn.
The plant produces tiny flowers in spring and summer, which are borne in slender, loose, panicled racemes at the end of stalks. The plant is dioecious (male and female flowers are borne on separate plants); male flowers are orange-yellow; female flowers are red-orange. Sheep Sorrel is wind-pollinated, shedding copious amounts of pollen. The pollen is dominant in the autumn. The seed is an achene and is dispersed by wind and insects. Sheep sorrel reproduces by seed or from creeping roots and rhizomes.
Sheep sorrel is common in lawns, fields, pastures, meadows and waste places, and along roadsides.
Sheep sorrel leaves are used in soups and salads, and can be chewed to quench thirst. They have also been used as herbal medication. Sheep sorrel contains selenium and oxalic acid, both of which can be poisonous in large quantities.
No allergens from this plant have yet been characterised.
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 family Polygonaceae. (1)
IgE mediated reactions
Sheep sorrel pollen can induce asthma, allergic rhinitis and allergic conjunctivitis. (2, 3, 4, 5)
In Poland, examination of the records of 8,576 patients with “upper airway” allergy documented hypersensitivity to weed pollen allergens in 12.5%, the most prevalent sensitisation being to Wormwood (86.2%), Mugwort (82.9%), White Goosefoot (44.3%) and Sheep Sorrel (19.0%). Hypersensitivity to grass, tree and/or shrub pollens coexisted in 85.5%. (2) Sorrel has been shown to also be important pollen in eastern Poland. (6)
Sheep Sorrel pollen has also been shown to be a common aeroallergen in London, Leiden, Brussels, Munich and Marseilles (7), as well as in Athens (8) and Zurich. (9) Pollen from the Rumex species has been recorded as a significant aeroallergen in Salamanca (10), Murcia (11) and Seville, (12) Spain, but was found to be in low concentrations in the atmosphere in Madrid. (13)
Various studies in North America have demonstrated the presence of Rumex pollen: in the Tampa Bay area, Florida, (14) the Gulf Coast, (15) Anchorage, Alaska, (16) Philadelphia, Pennsylvania, and Cherry Hill, New Jersey. (17) In a study in Westchester County in the state of New York of skin prick tests to 48 aeroallergens in100 patients referred for allergic rhinitis, 3% had a positive skin prick test for Sorrel. (18) In a study examining the prevalence of positive skin test responses in a symptomatic military population of 1137 patients aged 4-79 years old who underwent a standard skin-prick testing panel of 53 aeroallergens, 18% were positive to Dock / Sorrel. (19)
In this study of pollen allergy in Taiwan, 419 patients with clinically diagnosed allergic rhinitis were enrolled and sensitisation to 30 allergens assessed by skin prick testing. A total of 313 (74.7%) had a positive skin test. The most common pollen allergens were spiny pigweed, Johnson grass, and sheep sorrel. (20) Sheep sorrel has also been documented to be an aeroallergen in Japan. (21)
Rumex pollen has been documented as an important aeroallergen in La Laguna City, Tenerife, in the Canary Islands (22), Dehra Dun, India (23) and Korea. (24)
The most prevalent aeroallergens was assessed in Mashhad City, the second largest city in Iran. Skin prick tests were performed with 27 common regional aeroallergens in 311 patients with allergic rhinitis. Forty three percent of patients were sensitised to Sheep sorrel. (25)
Rumex crispus, a member of the family, was detected in a sandstorm in Riyadh, Saudi Arabia. Sandstorms are potential triggers of asthma. (26) Other close relatives, Rumex vesicarius (27) and Rumex acetosa (28) (garden sorrel), have been shown to be important aeroallergens.
Fatal oxalic acid poisoning from Sorrel soup has been reported. (29)
Compiled by Dr Harris Steinman, email@example.comUpdated: 30/09/2008
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