Latin name: Pseudotsuga taxifolia
Source material: Pollen
Common names: Douglas fir tree, Oregon pine, yellow fir
Of the 6 species of Pseudotsuga, 2 are native to North America, 1 to Mexico, and 4 to Asia and parts of Europe.
The Douglas fir is a tall, evergreen timber tree, with short needles and egg-shaped cones similar to those of a fir tree, but it is not a true fir. Douglas fir attains a height of 30 to 90 m. The trees have irregularly whorled branches. The foliage is feathery-soft and not sharp. Colour varies from silver to heavy bluish-green. Branchlets are nearly smooth, but not as smooth as the branches of firs.
Flowers are monoecious (individual flowers are either male or female, but both sexes are found on the same plant) and bloom in May. The fruit is a pendulous cone with 3-lobed bracts extending beyond the cone scales. The fruit is very distinctive, and – when present – is the best identification feature.
This is the most important timber tree of western North America, and is also widely planted in parts of Europe. The timber is usually called Oregon pine or yellow fir.
No allergens from this plant have yet been characterised.
Extensive cross-reactivity between the different individual species of the genus could be expected. (1)
IgE mediated reactions
Anecdotal evidence suggests that asthma, allergic rhinitis and allergic conjunctivitis, similar to reactions caused by other members of this family, are possible following exposure to pollen from this tree; however, no specific studies have been reported to date.
The Douglas fir is not an important allergen in urbanised communities – except those situated close to Douglas fir plantations, where the prevalence of atopic sensitisation to pollen from this tree is expected to be high.
The tussock moth caterpillar, occurring in forested areas of Oregon, was associated with itching of the skin and eyes, nasal discharge, cough, and, at times, respiratory difficulty in 41 of 428 individuals working in a forest. (2)
Compiled by Dr Harris Steinman, email@example.com
- Yman L. Botanical relations and immunological cross-reactions in pollen allergy. 2nd ed. Pharmacia Diagnostics AB. Uppsala. Sweden. 1982: ISBN 91-970475-09.
- Press E, Googins JA, Poareo H, Jones K. Health hazards to timber and forestry workers from the tussock moth. Arch Environ Health 1977;32(5):206-210.