House dust mite (HDM) allergen levels in Sydney beds are determined by the season, with new research discovering fluctuations of such magnitude between summer and autumn levels they may be sufficient to influence asthma symptoms in sufferers.
A Sydney study involving over 500 children has found HDM allergen levels to be at their minimum in summer and increasing approximately 2-3 fold during late autumn.
This annual cycle was observed over seven years and partly determined by relative humidity. Results were measured using dust samples collected from the children's beds on 13 occasions, and relative humidity and temperature were recorded.
Researcher Daniel Crisafulli, from the Woolcock Institute of Medical Research explains the study was part of the Childhood Prevention Asthma Study (CAPS) conducted between 1997 and 2004.
"Such fluctuations are probably unavoidable and should serve as a reminder that people with asthma should be monitoring the severity of their symptoms and implement their asthma action plans" he said.
"The results provide the most comprehensive set of observations to date on seasonal fluctuations of mite allergens in children's beds with climate.
"There was some variation in the annual timing of peaks, depending on the preceding seasonal climate. Allergen peaks could also be correlated with humidity peaks two months earlier, as humidity has an effect on the mite population.
Mr Crisafulli points out that other factors such as viral infections are known to be important causes of severe asthma attacks and that the interaction between seasonal allergen levels and viruses will be examined in a future study.
The research paper will be published in the December issue of Allergy.