Hay fever cases soar because warm summers mean there’s more pollen
HAy fever cases are rising because plants are producing more pollen for longer, a study into allergies has found.
Previously scientists have blamed an ‘allergy epidemic’ in the developed world on our increasing obsession with cleanliness and greater urban pollution.
But the same study found that allergies to pet hair and mould are staying stable – leading researchers to pin the blame on pollen.
They suggest that our increasingly warm summers mean plants are able to produce pollen for longer.
The team from Sweden found that allergic reactions to grass pollen among adults has risen from 26 per cent to 39 per cent between 1992 and 2012. One in four adults in Sweden now has hay fever – the same level as the UK, said the academics from the Sahlgrenska Academy, University of Gothenburg.
However, there were no statistically significant changes in fur, mites or mould allergies over the same period.
Researcher Anders Bjerg said: ‘Levels of both grass and birch pollen increased during the study period and ... the length of the pollen season has increased.
‘It is a possible explanation for the singular increase in allergic sensitization to pollen.’
The rise in pollen may be down to warmer weather – since the 1970s there has been an average summer temperature increase of 1.5C. Writing in the journal Clinical and Experimental Allergy, the researchers said: ‘A clear increase in pollen concentrations was observed together with a rise in mean temperature during spring and summer.’
The same is likely to apply to the UK, as pollen levels have also increased due to warmer temperatures, according to the National Pollen unit at Worcester University.
To calculate the increase in pollen sensitivity, the authors used skin-prick and blood tests from 788 subjects aged 16 to 60, from a larger group from a survey on asthma and allergies. The results were compared to those of the European Community Respiratory Health Survey sample aged 20 to 46 from the same area in 1991–1992.