House dust mites identified as the main cause of respiratory allergies in S'pore

SINGAPORE - Scientists and clinicians from A*STAR's Singapore Immunology Network (SIgN) and the National University of Singapore (NUS) have discovered that the primary cause of respiratory allergies in Singapore is the exposure to the house dust mite.

The new study also revealed that close to 15 per cent of Singapore's adult population are being affected by asthma and nearly 40 per cent are troubled by allergic rhinitis.

According to the World Health Organisation, it is estimated that approximately 300 million people suffer from asthma worldwide and even more are affected by allergic rhinitis. Both conditions are now increasingly common in Southeast Asian populations.

The research team conducted a large scale cohort study with approximately 8,000 participants. Reactivity to 12 common allergens was evaluated by a skin prick test or by measuring the level of allergy-associated Immunoglobulin E (IgE).

IgE is a class of antibodies that is raised upon reaction to an allergen.

The findings showed that approximately 80 per cent of those surveyed were reactive to house dust mites, and only minor reactivity to any other allergen. This high rate of reactions from house dust mites are strongly correlated with increased rates of allergic rhinitis and asthma in Singapore.

The study further found that participants who originate from non-tropical countries had low sensitisation rates for house dust mites when they first arrived in Singapore, but these rates increased as they spend more time here.

This increase was accompanied by an increase in airway allergies. Migrants from countries that have similar tropical climate, such as Malaysia, showed comparable rates as Singaporeans, pointing again to house dust mites as primary environmental cause.

These findings address the widening problem of allergy and asthma in tropical countries. The results suggest that changes in lifestyle resulting in more time spent indoors increase our exposure to high loads of house dust mite allergens, which translates into a dominant cause of respiratory allergic diseases in Southeast Asia.

The results potentially pave the way for the development of more effective allergen-specific desensitisation strategies as well as environmental interventions aiming at the reduction of the house dust mite-load.

"Knowing the cause is the first step in developing more effective interventions to improve the quality of life for asthma and allergic rhinitis sufferers," said Research Associate Professor Wang De Yun from the department of Otolaryngology at the NUS Yong Loo Lin School of Medicine.

The findings of the study were published as open access in the latest issue of the journal Allergy.