Passive exposure to bleach at home has been linked to higher rates of infection in children, according to new research.
A study led by the University of Leuven - KU Leuven - in Belgium found the chance of an episode of flu was 20% higher and recurrent tonsillitis 35% greater amongst children whose parents used bleach to clean their home.
Similarly, the risk of any recurrent infection was 18% higher amongst children of regular bleach users.
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Researchers said "the high frequency of use of disinfecting cleaning products - caused by erroneous belief, reinforced by advertising, that our homes should be free of microbes - makes the modest effects reported in our study of public health concern".
They calculated the results by looking at the potential impact of exposure to bleach in the homes of more than 9,000 children between the ages of six and 12 attending more than 50 different schools in the Netherlands, Finland and Spain.
Their parents were asked to complete a questionnaire on the number and frequency of times their children had flu, tonsillitis, sinusitis, bronchitis, otitis (ear infection) and pneumonia in the preceding 12 months. They were also asked if they used bleach to clean their homes at least once a week.
Use of bleach was common in Spain (72% of respondents) but rare in Finland (7%).
The study, which is published in the British Medical Journal, also noted that all Spanish schools were cleaned with bleach, while Finnish schools were not.
Researchers said after taking into account a number of influential factors, such as passive smoking at home, the presence of household mould, and whether bleach was used in the children's schools, overall the prevalence of infections, both single or recurrent, was higher in children of bleach users.
They said these were statistically significant for flu, tonsillitis, and any infection.
But they added that it is purely an observational study, so no definitive conclusions can be drawn about cause and effect.
The authors said their findings were in line with the increased risk of recurrent bronchitis in school-age children reported in a Belgian cross-sectional study.
"Domestic cleaning involves exposure to a large variety of irritants and sensitising chemicals that are used following certain cleaning patterns," the study said.
"Unfortunately, we did not have information on the use of other cleaning products and we cannot exclude the possibility that the observed results are due to the use of other irritants or to their combinations."