The study, published in the journal Thorax, found indoor mold may have a link with asthma. However, the researchers said more work is needed in this area before definitive conclusions can be drawn.

The Cardiff University researchers asked patients with asthma living in two areas of South Wales if they noticed mold growing inside their houses. Mold growth was then confirmed by a trained observer.

In half of the houses with mold -- chosen at random -- the mold was removed. Fungicidal wash was used to kill any remaining mold and ventilation was improved by means of a fan in the loft.

In the other houses, mold removal was delayed for 12 months.

"In the houses where mold was removed, the symptoms of asthma improved and the use of inhalers decreased more than in the other houses," Dr. Michael Burr of Cardiff University's School of Medicine said in a statement. "Removing mold also led to improvements in other symptoms: sneezing, runny or blocked noses, and itchy-watery eyes."