Last year we were all scared by the idea that Calpol had been deemed the ‘heroin of childhood’, but now it has also been linked to asthma.

Children who take paracetamol during their first two years of life may be at a higher risk of developing asthma by the age of 18.

Research presented at the European Respiratory Society International Congress in Paris showed the link between paracetamol use and asthma seemed strongest in those who had a particular variant of the glutathione S-transferase (GST) gene, GSTP1.

But the study authors stressed the findings showed only that there was an association between paracetamol and asthma, not that paracetamol caused the lung condition.

Paracetamol is recommended by the NHS to treat most kinds of childhood ailments, including headache, stomach ache, ear ache, and cold symptoms, while it can also be used to reduce fever. The leading brand is Calpol.

The research, carried out at the University of Melbourne, Australia, looked at 620 children who had been followed from birth to 18 years old as part of the Melbourne Atopy Cohort Study.

They had been recruited to the study before they were born because they were considered to be potentially at high risk of developing an allergy-related disease as they had at least one family member (mother, father or sibling) with a self-reported allergic disease (asthma, eczema, hay fever or a severe food allergy).

After their birth, a research nurse rang the family every four weeks for the first 15 months, and then at 18 months and at two-years-old to ask how many days in the previous weeks had the child taken paracetamol.

When the children were 18 years old they gave a blood or saliva sample, which was tested for variants of the GST genes: GSTT1, GSTM1 and GSTP1.

Commenting on the study, Neil Pearce, professor of epidemiology and biostatistics at the London School of Hygiene and Tropical Medicine, said: "The idea that paracetamol use early in life may increase the risk of developing asthma has been around for about 20 years. It has been extraordinarily difficult to prove or disprove.”