Latin name: Elaeagnus angustifolia
Source material: Pollen
Common names: Russian olive, Russian silverberry, Oleaster, Silverberry
The Russian olive tree is a member of the family Eleagnaceae. The tree is native to Europe and western Asia. The genus Elaeagnus comprises roughly 40 species of shrubs and small trees. Only Silverberry, Elaeagnus comutata, is native to North America; it is found primarily in eastern Canada. Buffaloberries, Shepherdia spp., are other native Elaeagnaceae family members found across Canada and extending down into the western United States (1-3).
The Russian olive tree was introduced into North America in the late 1800s. It was frequently planted on the Great Plains in rows for windbreaks (1), and was subsequently naturalised into the wild. The tree has invaded zones along watercourses in many arid and semiarid regions of the world. It is also used as an ornamental tree in many European cities for its gray foliage and tolerance of salty soil (4).
It is a tall shrub or small tree, 5 to 8 m in height, erect or (frequently) leaning, twisted, or distorted. It has low branches and an open crown. The branches are reddish brown, with 2- to 5-cm thorns. The leaves are alternate, 5 to 8 cm long, narrow, and light-green on top. The stems, buds, and the under surface of the leaves have a dense covering of minute, silvery to rust-coloured scales (5).
The flowers are 4-lobed, 1 cm long, yellow within and silvery gray outside, and very fragrant and rich in honey. They are produced in clusters of 1-3. The fruit is a small cherry-like drupe, 1-1.5 cm long, orange-brown and covered in silvery scales (5). The fruit is edible and sweet, with a dryish, mealy texture.
Although the tree is pollinated mainly by insects, Russian olive pollen can be identified in air samples, especially during the May to June pollination season, and skin test positivity to Elaeagnus has been demonstrated in hayfever patients in both the Midwest and West of the US (1,4).
In Madrid, Spain, the pollination of Russian olive occurs from May to June, coinciding with the pollination period of Olive trees and grasses. Pollen counts of Russian olive at local pollen stations may be low, but must be considered in the context of the relatively large size of the pollen in comparison with other allergenic pollens such as grass or Olive (4). Although a city or other area may not be widely planted with this tree, the local distribution of the pollen may severely affect sensitised individuals.
In Europe, the fruits, called ”Trebizond grapes,” are dried and used in cake-making. The wood is hard and fine-grained (1).
In a study of 134 patients in Madrid, major IgE-binding bands in Russian olive extract, with molecular weights of 37, 43, 63.7 and 77.4 kDa, were recognised in 40%, 65%, 50% and 45% of patients, respectively (4).
No allergens have been characterised to date.
In 103 Michigan residents with symptoms suggestive of allergic rhinitis or asthma, who were skin-tested with Olive tree (Olea europaea) pollen extract, 19 had positive reactions. As the Olive tree is not present in this area, an evaluation was made as to whether these findings were the result of cross-reactivity among the tree pollen allergens from Olive, Ash (Fraxinus americana), Privet (Ligustrum vulgare), and Russian olive. On ELISA testing, 11 of the 19 skin-test-positive patients were Olive positive, 8 were positive to Ash, 7 to Privet and 10 to Russian olive, and inhibition studies demonstrated that all 3 of these tree pollens were capable of inhibiting the binding of IgE in a dose-response fashion. Several proteins common to Olive, Ash, and Privet were demonstrated. Of the 12 Olive skin-test-positive patients contacted, 75% confirmed exposure to 1 or more of the studied trees in their yards (6).
In a study conducted in Madrid, Spain, all patients with a positive skin test to Russian olive were also positive to Olive; but not all Olive-positive patients were positive to Russian olive. In inhibition studies, the Russian olive extract was not able to inhibit Olive, whereas an Olive extract inhibited Russian olive by up to 41%, establishing minimal to moderate cross-reactivity between Olive tree and Russian olive tree, but not excluding cosensitisation. The presence of Ole e 1- and Ole e 4-like allergens in Russian olive tree extract was confirmed (4,7).
Although only sparse reports document sensitisation to Russian olive tree, anecdotal evidence suggests that asthma and hayfever are possible following exposure to pollen from this tree (1,4-5).
In a study of 134 patients in Madrid with rhinoconjunctivitis and/or asthma, 73 (30.5%) were found to have a positive skin test to Russian olive tree, and all were positive to Olive (Olea europaea) as well. A nasal challenge with Russian olive tree was positive in 3 of 6 patients with a positive skin test to both pollens, and negative in 5 patients with a positive skin test to Olive tree only (4).
It has been suggested that a positive skin test to Olive pollen in regions where Olive trees are not present may be due to a sensitisation to Russian olive or other cross-reactive pollens (5).
Compiled by Dr Harris Steinman, firstname.lastname@example.org.
Weber RW. Russian olive. Ann Allergy Asthma Immunol 2004;92(1):A6
Farrar JL. Trees of the Northern United States and Canada. Ames, IA: Iowa State University Press; 1995:407
Lewis WH, Vinay P, Zenger VE. Airborne and Allergenic Pollen of North America. Baltimore, MD: Johns Hopkins University Press; 1983:39-41,189
Sastre J, Lluch-Bernal M, Bustillo AM,
Carnes J, Maranon F, Casanovas M, Fernandez-Caldas E. Allergenicity and cross-reactivity of Russian olive pollen (Eleagnus angustifolia). Allergy 2004;59(11):1181-6
Wikipedia contributors, ”Elaeagnus angustifolia”, Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Elaeagnus_angustifolia&oldid=204287448 (accessed July 7, 2008)
Kernerman SM, McCullough J, Green J,
Ownby DR. Evidence of cross-reactivity between olive, ash, privet, and Russian Olive tree pollen allergens.
Ann Allergy 1992;69(6):493-6
Carnes J, Fernandez-Caldas E. Ole e 4 and Ole e 5, important allergens of Olea europaea. Allergy 2002;57 Suppl 71:24-8