In theory, lowering indoor humidity should lower concentrations of moisture-loving dust mites – a major trigger for asthma-related breathing problems.
To test this,
Specialists retrofitted each home with a humidity-lowering ventilation system. They also steam-cleaned carpets, and replaced mattress covers and bedding, to clear dust mites.
In half the homes the ventilation systems actively exchanged indoor and outdoor air. In the other “control group” half, the systems had operational motors but non-operational fans to help ensure the groups remained “blinded” to what was actually happening, the researchers report in the journal Allergy.
Also, their comparison of morning breathing tests done at the start of the study and again at 3, 6, 9, and 12 months, showed no difference between those living with or without operational ventilation.
However, participants living in homes with working ventilation systems showed an overall significant improvement in evening breathing tests, while those with non-working systems worsened in these tests.