Occupational allergen

A wood from a tree species, whose dust may frequently induce hayfever, asthma and conjunctivitis in sensitised individuals.

Allergen Exposure

Geographical distribution

This tree is widely distributed in tropical West Africa, from Guinea to Cameroon. It can be 50 m or more in height and has a straight trunk clear to over 20 m, and high buttresses. The trunk diameter may exceed 1.5 m. The growth ring boundaries are distinct. The wood is yellow, white, grey or olive, with no difference between heartwood and sapwood. The texture is medium to coarse. The wood has an unpleasant smell when green, but this usually does not persist after drying.

Environment

The tree occurs predominantly along waterways and on abandoned farms in the transition zone between the humid evergreen and semi-deciduous forests.

Its soft wood is widely used, especially in the East, mainly for purposes for which strength and durability are not important. It is useful in framing, particle-, block- and fiber-board, boxes, crates, planks, model making, some furniture components, millwork, patternmaking, plywood, sauna benches and artificial limbs.

No allergens from this plant have yet been characterised.

Allergens appear to be 63.8, 57.5 and 28 kDa in size. A faint allergen band was also seen at 16.8 kDa (1).

IgE binding to proteins with molecular weights of 17 kDa and 28 kDa, and less intense binding to a band with an approximate molecular weight of 60 kDa, were detected (2).

An extensive cross-reactivity among the different individual species and genera of the family could be expected (3).

Four patients with occupational asthma were studied. All patients were exposed to African maple dust, and two of them were also exposed to Ramin dust. Skin tests and bronchial provocation tests with African maple extracts revealed an immediate response in all patients, and the same tests performed with Ramin extracts again revealed an immediate reaction in patients both exposed and not exposed to Ramin wood dust. Specific IgE antibodies against African maple extracts were demonstrated in all patients, as measured by a reverse enzyme immunoassay. Cross-reactivity between both woods was demonstrated by a reverse enzyme immunoassay inhibition study (4).

IgE-mediated reactions

Abachi wood dust may frequently cause occupational asthma, allergic rhinitis, allergic conjunctivitis, and contact urticaria(2, 4-10). Occupational allergic contact dermatitis has also been reported (11-12).

Abachi wood sensitivity may occur many years after initial contact with the wood. A 28-year-old man suffered from rhinitis and asthma 8 years after exposure to different woods, in particular Abachi wood. Skin-specific IgE tests were positive to Abachi wood extract, and serum-specific IgE was demonstrated. Specific nasal provocation and bronchoprovocation tests performed by exposure to fine Abachi wood dust were positive (13).

Abachi wood allergy may also produce delayed or dual responses following exposure. A 58-year-old Japanese man, a carpenter, with cough, rhinorrhea, wheezing, dyspnea and ocular itching occurring a few minutes after each exposure to the sawdust of Abachi wood, described a secondary response several hours later, although his symptoms improved soon after exposure. He was unaffected when working with any other woods. Skin- and serum-specific IgE to Abachi wood were detected. Bronchoprovocation with Abachi wood extract resulted in an immediate response, followed later with a secondary, delayed response (dual response) (14).

Not surprisingly, as Abachi wood is often used for the building of saunas, associated workers may become sensitised to the dust (15). A study reported on 2 carpenters who developed rhinitis, conjunctivitis, bronchial wheezing, and dyspnoea while working with Abachi wood for building saunas (16).

Contact urticaria may be associated with occupational asthma to Abachi wood dust. (4)4 A report of 8 patients with occupational asthma caused by Abachi wood sawdust described how these patients also presented with urticaria while working with this wood. Skin-specific IgE was detected in all. Specific IgE antibodies against Abachi wood could also be demonstrated by a reverse ELISA method. Skin provocation tests (via rubbing) on the 8 patients evoked a positive reaction within 20 minutes (17).

Allergic laryngitis following inhalation of Abachi wood dust has been described and was confirmed with provocation tests in which the patients displayed a change in vocal cord status (18).