Substance Info: (and synonyms)
White Ash tree

Background Info:

Family: Oleaceae.

The White Ash tree is an important allergen in urbanised communities, and rural communities situated near woodlands where this tree grows. In these places the prevalence of atopic sensitisation to pollen from this tree is expected to be high.

Fraxinus is a genus of about 65 species, which are distributed in the north temperate regions. White Ash is native and common in eastern North America, where it is often grown as a source of hardwood timber. It is hardy and thrives in Europe (Great Britain, Ireland, Scandinavia, Russia, Central and Southern Europe).

White ash is a tall, deciduous, long lived tree growing to a height of between18 and 40 metres high, it is the most common ash. It occurs in mixed forests. The ashes are ornamental trees with handsome foliage. The trunk is straight and free of branches for most of its length, and the crown is narrow and pyramidal when grown in a mixed stand. Open grown specimens have a short trunk with rounded crown. The bark is ash-grey to brown, with a diamond pattern. Older trees may be scaly. Leaves aer compound and 20 - 30cm in length. The flowers are born in panicles near branch tips. Winged fruits hang in bunches throughout the winter and are shaped like keys, which resemble helicopter blades when falling to the ground.

They are important timber trees, having light and elastic wood. The US exports ash timber all over the world. White ash is used as snakebite preventive.

White Ash grows best on deep, well-drained, moist soils with other hardwoods.

White Ash is dioecious (male and female flowers are distinct but grow on separate trees). Clusters of yellow-orange flowers appear in March to May, the male flowers blooming first and long before the leaf buds appear. It is one of the last trees to turn green and one of the first to drop leaves in the fall. Pollen season may start as early as January. Pollen shedding for an individual tree takes 3 or 4 days. Ash sheds copious amounts of pollen. Ash is entirely wind-pollinated and the pollen is moderately allergenic. The pollen is carried by wind as far as 110m from the point of dispersion. A good seed crop is produced about every third year; the minimum seed-bearing age is 20 years. The fruit matures from October to November and disperses over winter.


Adverse Reactions:


[ 1 / 6 ]

The daily pollen concentration measured in the atmosphere over a 6-year period in Badajoz, in southwestern Spain, demonstrated pollen from Fraxinus species to be one of the most important aeroallergens. (Silva Palacios 2000 ref.4732 9)

Silva Palacios I, Tormo Molina R, Nuñoz Rodríguez AF. Influence of wind direction on pollen concentration in the atmosphere. Int J Biometeorol 2000;44(3):128-33

[ 2 / 6 ]

In Cordoba, Spain, skin-prick tests were carried out on 1,500 pollen-allergic patients with an extract of Fraxinus pollen, and 59% were positive. The great majority of the patients were polysensitive; only 8% were found to be monosensitive. (Guerra 1995 ref.4784 9)

Guerra F, Galán Carmen C, Daza JC, Miguel R, Moreno C, González J, Domínguez E. Study of sensitivity to the pollen of Fraxinus spp. (Oleaceae) in Cordoba, Spain. J Investig Allergol Clin Immunol 1995;5(3):166-70

[ 3 / 6 ]

Although Ash tree pollen may not always be a major component of aeroallergens, because of cross-reactivity individuals who are Olive tree pollen-allergic may be found to be sensitive to Ash tree pollen. Thus in 503 patients with allergic rhinitis in the southern part of Switzerland (Canton Ticino) who were tested by skin-prick test for sensitisation to common allergens, of the 54% who were positive to Olive tree, a great many would be allergic to Ash tree pollen. (Gilardi 1994 ref.4549 9)

Gilardi S, Torricelli R, Peeters AG, Wüthrich B. Pollinosis in Canton Ticino. A prospective study in Locarno. [German] Schweiz Med Wochenschr 1994;124(42):1841-1847

[ 4 / 6 ]

Asthma, allergic rhinitis and allergic conjunctivitis result from exposure to pollen from this tree. (Kernerman 1992 ref.170 83) (Liccardi 1996 ref.81 948)

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

[ 5 / 6 ]

Allergic reactions, e.g., asthma, allergic rhinitis and conjunctivitis have been described. 80 patients sera were investigated. Specific IgE antibodies against ten various tree pollens were determined. It was found that birch, beech, Alder, hazel and oak pollens are most important as causes of springtime hay fever. 75% of patients had increased specific IgE-titres against these pollens whereas maple, poplar, elm, sallow and ash allergens more often gave negative or only weak positive test results. (Jung 1987 ref.3252 8) (Eriksson 1978 ref.3255 8) However, Beech pollen does not play the most significant role in causing hay fever. (Jung 1987 ref.3252 0)

Jung K, Schlenvoigt G, Jäger L. Allergologic-immunochemical study of tree and bush pollen. II--Study of the sensitization spectrum of patients with seasonal rhinitis in the spring. [German] Allerg Immunol (Leipz) 1987;33(4):215-21

[ 6 / 6 ]

Ash tree pollen has also been demonstrated to be an important aeroallergen in Zurich, Switzerland, contributing greatly to the overall pollen count. (Helbling 1985 ref.4405 8)

Helbling A, Leuschner RM, Wüthrich B. Pollinosis. IV. Which pollens should be tested in allergology practice? Results of determinations of allergy-causing pollens in the Zurich air 1981-1984, with reference to threshold concentrations. [German] Schweiz Med Wochenschr 1985;115(34):1150-1159

Occupational reactions

[ 1 ]

Dyspnoea in a a 42-year-old man following exposure to ash wood dust. Inhalation of ash wood dust (challenge test) elicited a very strong, immediate bronchospastic reaction, associated with profuse watery rhinorrhea, conjunctival congestion and lacrimation. (Szmidt 1994 ref.4430 0)

Szmidt M, Gondorowicz K. Bronchial asthma caused by exposure to ash wood dust. [Polish] Pol Tyg Lek 1994;49(14-15):343-344

Information supplied from an abridged section of:
Allergy Advisor - Zing Solutions

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