Introduction

The spectacular purple flowers of Tibouchina trees bloom at the same time as the less obvious ragweed, between February and May, and many people in Alstonville blame the pollen from Tibouchina trees for the cause of their late summer hayfever.

An extract of Tibouchina pollen was made by harvesting the stamens from Tibouchina flowers, drying the stamens and then sieving the pollen through a 53 sieve. The pollen was extracted in distilled water overnight, centrifuged and the supernatant filtered through a 0.2 Millipore membrane. No commercial Tibouchina extract is available.

Airborne pollen and the mould Alternaria have been monitored in Casino using a Burkard spore trap sited on the roof of the swimming pool complex, (courtesy of Casino council). ragweed pollen appears in late February, peaks during the first week in April with a count of 483/ m3 and declines to single figures by early May. The duration of the season and the pollen count is similar to that in Canada and the United States.

Validated questionnaires were filled in prior to testing 206 volunteers who fulfilled the study criteria.

The skin prick testing extracts used were: Dermatophagoides pteronyssinus and Dermatophagoides farinae (dust mites), cockroach, cat dander, Alternaria mould, Ryegrass, Bermuda grass, Paspalum grass, plantain weed, negative control (glycerol saline), positive control (histamine 10 mg/ml.), ragweed and Tibouchina pollen extracts.

Of those with positive SPT to either ragweed or Tibouchina, just over half (40) had symptoms of seasonal allergic rhinoconjunctivitis that coincided with the ragweed pollen season (February to May) and nine suffered with seasonal asthma. Tibouchina caused seasonal rhinitis but not asthma.

Plainly ragweed can be considered a serious airborne allergen. This study has demonstrated that Tibouchina is also an airborne allergen in Alstonville.

Allergic rhinitis is perceived by sufferers to impact on the quality of life to a greater extent than asthma. It causes significant discomforts with interrupted sleep, increased fatigue, irritability, lossof concentration as well as the physical discomforts of itching and watery nose and eyes and sneezing and blocking of the nose.

Reduction of indoor aeroallergen exposure is helpful in reducing perennial symptoms and is achievable. When antihistamines and topical corticosteroid nasal sprays fail to reduce symptoms of unavoidable outdoor allergen exposure, grass and ragweed pollen allergen immunotherapy injections can be helpful.

Dr Diana Bass Department of Immunology and Allergy Concord Repatriation Hospital