Double blind trial of ionisers in children with asthma sensitive to the house dust mite.

BACKGROUND

Manufacturers of ionisers claim many benefits from the use of their devices, including the relief of asthma. Particles removed from the air are likely to include airborne allergens, so ionisers may achieve an effect by reducing the allergen load.

METHODS

The effect of ionisers on airborne concentrations of house dust mite allergen Der p I was investigated in a double blind, crossover, placebo controlled trial in the homes of 20 children with allergic asthma. Subjects recorded their peak expiratory flow rate (PEFR) twice daily and completed a daily symptom score and treatment schedule on a diary card for two six week periods, one with an active ioniser and the other with a placed ioniser (randomly allocated) used in the living room and the bedroom.

RESULTS

Airborne Der p I concentrations fell significantly during the active period compared with the placebo period, but there was no significant change in PEFR, symptom scores, or treatment usage. There was an increase in night time cough which almost reached significance during the active period.

CONCLUSIONS

This study indicates that the use of ionisers cannot be recommended in the homes of asthmatic subjects to improve their symptoms. The significant reduction of airborne allergen concentrations may be of use as part of a multidevice allergen avoidance regimen, but the increase in night time cough requires further study.