t2 Grey alder

Allergens within Tree Pollens

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  • Latin name: Alnus incana
  • Family: Betulaceae
  • Common names: Grey Alder, Speckled Alder
  • Source material: Pollen
Related species:
  • A. incana ssp. tenuifolia - Thinleaf Alder
  • A. incana ssp. rugosa - Speckled Alder
  • A. rubra - Red Alder or Oregon Alder
  • A. rhombifolia - White Alder
  • A. glutinosa - Black Alder
  • A. cordata - Italian Alder
  • A. viridis - Green Alder
A tree species producing pollen, which often induces hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Grey Alder is the most widely distributed Alder in western North America and Europe.
 
Grey Alder is a rapidly growing, deciduous, multi-stemmed shrub or small tree, which tends to form thickets. It has a long trunk and a narrow crown. The Alder typically grows between 2 and 5 m in height, but may reach 12 m. The bark is thin, smooth, and green-grey, greyish-brown, or reddish-brown. Trees often produce adventitious roots from near the base of the stem. The leaves are broadly elliptic or ovate, and dull green on both sides. Leaves remain green until they are dropped in the fall.
 
Flowering generally begins during March and April, with seeds ripening from September to November. The flowers occur in catkins and are monoecious (individual flowers are either male or female, but both sexes are found on the same plant). Alders are wind-pollinated and produce clouds of yellow pollen. The cones remain on the plants for about a year after the seeds are shed, aiding in identification during winter. The fruit is a small, single-seeded nutlet, with narrow lateral wings.
 
Environment
Grey Alder seldom grows away from water. It is typically found bordering streams, rivers and mountain springs, on moist lowlands and in swamps. It invades gaps and clearings in forests and thrives there.
 
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 (1). 

Clinical Experience

IgE mediated reactions
Alder pollen can cause asthma, allergic rhinitis and allergic conjunctivitis (2-3).
 
Grey Alder tree pollen is a frequent cause of allergic symptoms. In the southern part of Switzerland, in 503 patients with allergic rhinitis tested by skin-prick test for sensitisation to common allergens, 33% were sensitised to Alder tree pollen (3).
 
In central Italy, the pollination period stretches from February to mid-October. Pollen from the Alder is particularly high in the month of March (4).
 
Alder pollen has also been shown to be a frequent aeroallergen in studies in Spain (5-6).
 
Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09
    2. Wuthrich B, Annen H. Pollionosis: I. Findings on the clinical aspects and the pollen spectrum in 1565 pollen-sensitive patients. [German] Schweiz Med Wochenschr 1979;109(33):1212-8
    3. Gilardi S, Torricelli R, Peeters AG, Wuthrich B. Pollinosis in Canton Ticino. A prospective study in Locarno. [German] Schweiz Med Wochenschr 1994;124(42):1841-1847
    4. Murgia M, De Dominicis V, Cresti M. The pollen calendar of Siena (Central Italy). Allergol Immunopathol (Madr) 1983;11(5):361-5
    5. Silva Palacios I, Tormo Molina R, Nunoz Rodriguez AF. Influence of wind direction on pollen concentration in the atmosphere. Int J Biometeorol 2000;44(3):128-33
    6. Hernandez Prieto M, Lorente Toledano F, Romo Cortina A, Davila Gonzalez I, et al. Pollen calendar of the city of Salamanca (Spain). Aeropalynological analysis for 1981-1982 and 1991-1992. Allergol Immunopathol (Madr) 1998;26(5):209-22

2002



Further Reading