Asthma sufferers who remove mould from their homes could see an improvement in their symptoms, a Cardiff University study has found.
Symptoms of asthma include sneezing and runny noses
Half of the south Wales homes used in the research were cleaned of mould and ventilation was improved, and the other half were left mouldy for 12 months.
Asthma patients in the mould-free homes used their inhalers less and symptoms like sneezing lessened, said experts.
Charity Asthma UK said it wanted more research before conclusions were drawn.
Researchers at Cardiff University's School of Medicine studied 182 people with asthma living in 164 mouldy houses in two locations in south Wales.
Michael Burr, of the department for primary care said the removal of mould in half of the houses led to improvements in asthma symptoms, including runny or blocked noses and itchy-watery eyes.
He added: "There was no clear effect on measurements of breathing, but this may have been because patients used their inhalers as needed so that they could always breathe freely."
Jenny Versnel, Asthma UK's executive director of research and policy, said the study highlighted the importance of keeping houses dry and well ventilated.
"This can reduce exposure to certain asthma triggers such as mould spores which are found in damp places," she said.
Asthma UK figures show the prevalence of asthma in Wales is among the highest in the world, with 260,000 people receiving treatment, with the rate of hospital admissions for adults 12% more than anywhere else in the UK.
The study was funded by Asthma UK, the Medical Research Council, and the Wales Office of Research and Development.
The research has been published in the September edition of the medical journal Thorax.