Using household cleaning sprays and air fresheners as little as once a week increases the risk of asthma, according to an international study.
Heavy use of such products has previously been linked with occupational asthma, but the latest work suggests occasional use in the home also poses a threat.
The study of more than 3,500 people is published in the American Journal of Respiratory and Critical Care Medicine.
The risk of developing asthma increased with frequency of using spray cleaner in the household.
Spray air fresheners, furniture cleaners and glass cleaners carried the highest risk, although products not applied in spray form were not associated with asthma.
Exposure to cleaning products could account for as much as 15%, or one in seven adult asthma cases.
On average, the risk was 30-50% higher in people who regularly used the sprays than in others, and the incidence of doctor-diagnosed asthma was higher among those using sprays at least four days per week.
The study authors, Dr Jan-Paul Zock and colleagues from the Municipal Institute of Medical Research in Barcelona, said more work was needed to determine the biological mechanism behind the increased risk, however they suggest it may be that sprays contain irritants specific to asthma.
Dr Victoria King, research manager at Asthma UK, said: "We know that up to 25% of people exposed to chemicals, including cleaning sprays, at work will go on to develop occupational asthma. However, this report also highlights significant findings regarding the link between asthma and the use of spray cleaning products in the home.
"Although further research is needed, we do already know that air fresheners and bleach trigger symptoms in people who already have asthma. For anybody concerned about developing asthma as a result of using cleaning products we recommend they speak to their doctor or call our Adviceline on 08457 01 02 03."