Children who took paracetamol at least once a month had triple the risk of developing asthma compared with children who had never taken it, a study in The Lancet showed.
The findings follow a UK study, published last month in the European Respiratory Journal, which found that adults who took paracetamol weekly were nearly three times more likely to have asthma.
Calpol: paracetamol use in children should be limited, say experts
What is the research?
Findings are based on an international study of 205,487 children, aged six and seven, selected from 31 countries. Parents of the children were asked to complete a questionnaire about their child's symptoms of asthma, hay fever and eczema.
They were also asked whether paracetamol was given in the first year of life and the frequency of use in the past 12 months, as well as exposure to any other allergy risk factors such as pets or traffic.
Children who had been given paracetamol in the first year of life were 46 per cent more likely to develop symptoms of asthma when aged six or seven than children who had not taken paracetamol.
Children who took paracetamol once per year were 1.61 times more likely to develop asthma, but children who took paracetamol once a month were 3.23 times more likely to show asthma symptoms.
Paracetamol use in the first year of life increased the risk of hay fever by 48 per cent and eczema by 35 per cent.
Researchers propose that paracetamol use could result in depletion of glutathione and glutathione-dependent enzymes which offer protection against harmful oxidative stress caused by allergic stimuli.
What do the researchers say?
Lead researcher Professor Richard Beasley, from the Medical Research Institute of New Zealand, stressed that paracetamol use in children should not be stopped, but limited to use in children with a high fever, 38.5 degsC and above.
'Asthmatic children should continue to use paracetamol. We are planning more controlled trials of paracetamol-use in infancy and in adults with asthma,' he added.
What do other researchers say?
Leanne Male, assistant director of research at the charity Asthma UK, said: 'We still don't know how important different lifestyle and genetic factors are in affecting the development of asthma, so if we can establish the mechanisms behind how paracetamol might affect it, this could go some way towards helping to prevent the condition in the first place.'
The Lancet 2008; 372:1,039-48.
- Paracetamol use in childhood increased the risk of asthma, hay fever and eczema.
- Researchers stress the findings do not constitute a reason to stop using paracetamol in childhood.
- Randomised, controlled trials into the long-term effects of paracetamol use are needed.