t18 Eucalyptus, Gum-tree

Allergens within Tree Pollens

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  • Latin name: Eucalyptus spp
  • Family: Myrtaceae
  • Common names: Blue Gum tree, Eucalyptus, Fever tree
  • Source material: Pollen
Other members of the Eucalyptus genus:
  • E. camaldulensis (Red Gum)
  • E. citriodora (Lemon-scented Gum)
  • E. coccifera (Tasmanian Snow Gum)
  • E. dalrympleana (Mountain Gum)
  • E. ficifolia (Red Flowering Gum)
  • E. globulus (Tasmanian Blue Gum)
  • E. gunnii (Cider Gum)
  • E. johnstonii (Yellow Gum)
  • E. leucoxylon (White Ironbark)
  • E. pauciflorasubsp. niphophila (Snow Gum)
  • E. perriniana (Spinning Gum)
  • E. sideroxylon (Red Ironbark)
  • E. urnigera (Urn Gum)
  • E. amygdalina (Black Peppermint)
  • E. piperata (Sydney Peppermint)
A tree species producing pollen, which may induce hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution
Members of the Eucalyptus species are quick-growing evergreen trees or shrubs. Some species can reach heights over 135m. The colourful bark of the stems and trunks of the Eucalyptus may be dappled in gray, green, russet, or cream and may peel in sheets. These trees have leathery, smooth, lance-shaped leaves, which are studded with glands containing a fragrant volatile oil, thus resulting in a distinctive aroma.
 
Eucalyptus spp. originated in Australia. There are over 700 species of the tree, which now grows in almost all tropical and subtropical areas and is cultivated in many other climates, including North and South Africa, India, Southern Europe, California in the USA, and around the Mediterranean.
 
Their puffball-like flowers may be red or orange and have no petals, but instead numerous stamens arising from a capsule-like calyx, which give them their fluffy appearance. Eucalyptus flowers in the tropics almost year-round.
 
Environment
Eucalyptus thrives in any environment having a mean annual temperature not below 60 degrees F. Whole Eucalyptus forests have been planted in California and around the Mediterranean to help stem erosion. It has been planted in swampy areas, where its fast growth demands much water, thus performing a draining function.
 
Different species of Eucalyptus tree are grown for timber, paper, oil and gum production. The oils of the leaves and shoots are used for medicinal purposes: for example, an ingredient in tablets for soothing sore throats. The oils may be divided roughly into three classes of commercial importance: (1) the medicinal oils, which contain substantial amounts of eucalyptol (also known as cineol); (2) the industrial oils (contains terpenes); (3) the aromatic oils. Tannin is extracted from the bark of some varieties.
 
Unexpected exposure
The oils of the leaves and shoots are used for medicinal purposes, industrial oils (containing terpenes), and the aromatic oils. Tannin is extracted from the bark of some varieties.
 
Allergens
No allergens from this plant have yet been characterised.

Potential Cross-Reactivity

A high degree of cross reactivity among the different Eucalyptus species can be expected, and occasionally also to the species of the genus Melaleuca (1).

Clinical Experience

IgE mediated reactions
Eucalyptus pollen may result in symptoms of asthma, hayfever and conjunctivitis (2-3).
 
Eucalyptus pollen has been shown to be an important airborne allergen in Taiwan, with 76% of 195 children aged between 5 and 15 years demonstrating specific IgE to this pollen in their serum (2). Specific assays to determine specific IgE to Eucalyptus pollen has been shown to be effective (3).
 
Contact urticaria due to Eucalyptus pollen has been reported(4).
 
Other reactions
Eucalyptus oil is distilled from the fresh leaves of Eucalyptus globulus and other species. It may result in toxicity when ingested orally. A 6-year-old girl presented with slurred speech, ataxia and muscle weakness progressing to unconsciousness following the broad application of a home remedy for urticaria containing Eucalyptus oil (5).
 
Euproctis edwardsi, the mistletoe browntail moth, is a variety of hairy caterpillar widely distributed in southeastern Australia. Itching urticarial wheals and papular eruptions can follow contact with the caterpillars or their detached hairs.
 
Infestation with Euproctis edwardsi can be minimized by removal of mistletoe from Eucalyptus trees (6).

Compiled by Dr Harris Steinman, harris@zingsolutions.com

References:

    1. Yman L. Botanical relations and immunological cross-reactions in pollen allergy. Pharmacia Diagnostics AB. Uppsala. Sweden. 1978: ISBN 91-7260-511-1 
    2. Wang JY, Chen WY. Inhalant allergens in asthmatic children in Taiwan: comparison evaluation of skin testing, radioallergosorbent test and multiple allergosorbent chemiluminescent assay for specific IgE. J Formos Med Assoc 1992;91(12):1127-1132 
    3. Tang RB, Wu KK. Total serum IgE, allergy skin testing, and the radioallergosorbent test for the diagnosis of allergy in asthmatic children. Ann Allergy 1989;62(5):432-435 
    4. Vidal C, Cabeza N. Contact urticaria due to Eucalyptus pollen. Contact Dermatitis 1992;26(4):265 
    5. Darben T, Cominos B, Lee CT. Topical Eucalyptus oil poisoning. Australas J Dermatol 1998;39(4):265-267 
    6. Dunlop K, Freeman S. Caterpillar dermatitis. Australas J Dermatol 1997;38(4):193-195 

2002



Further Reading