Children who received acetaminophen in their first two years of life may be at increased risk of asthma, according to a study.
The NHS recommends the use of paracetamol to treat most childhood ailments, such as headache, stomach pain and cold symptoms, and can also be used to reduce fever. The leading brand is Calpol.
The researchers looked at 620 children who were considered at high risk of allergic disease because they had a family member with diseases such as asthma, eczema, hay fever or a severe food allergy.
Administering Calpol to children under two years of age may increase the risk of developing asthma, according to an important study
They called the families every four weeks for the first 15 months, then at 18 months and at two years to ask how many days the child had had paracetamol in the previous weeks.
When the children reached 18 years of age, they gave a blood or saliva sample that was analyzed for variants of the GST gene that protects the cells.
The researchers found that a variant of the GSTP1 gene was associated with almost double the risk of developing asthma.
PhD student Xin Dai said: "We found that children with the variant … had a 1.8 times higher risk of developing asthma at the age of 18 years.
"Our findings provide more evidence that the use of paracetamol in childhood can have an adverse effect on the respiratory health of children with particular genetic profiles and could be a possible cause of asthma.
One teacher said: "The problem is that children do not receive paracetamol early in life for no reason, they are often given because they have a respiratory infection.
"There is growing evidence that the GST gene superfamily, which includes three major classes … are associated with several diseases, including cancers, asthma, atherosclerosis, allergies, Alzheimer's and Parkinson's disease." Our study adds to this set of tests ".
However, Professor Neil Pearce, of the London School of Hygiene and Tropical Medicine, said: "The problem is that children do not receive paracetamol early in life for no reason, they are often given because they have a respiratory infection.
"It may be the infection that increases the risk of asthma, not paracetamol."
The study of the University of Melbourne was presented to the International Congress of the European Respiratory Society in Paris.
Johnson & Johnson, the makers of Calpol, did not respond to a request for comment.