US study finds increase in road crashes when pollen count high linking to hay fever

People with hay fever may be more likely to crash their car when the pollen count is high, a study suggests.

Scientists have found that, on days when pollen levels are soaring, there is a six per cent increase in fatal road accidents.

For every one per cent rise in the amount circulating in the air from flowers, grass and trees, the number of crashes rose by two per cent.

This suggests that allergy symptoms, such as sneezing and itchy eyes, could impact driving ability in a similar way to drinking alcohol, the researchers said.

One theory is that a high pollen count may impair some people’s cognitive ability – increasing the time it takes for them to react and shortening their attention span, so they are more distracted.

The researchers, from Wayne State University in the US city of Detroit, said: “This is the first study [on] the extent to which allergies due to seasonal pollen affect traffic fatalities.

“We find novel evidence that traffic fatalities increase on days in which the local pollen count is particularly high.

These effects are driven by cognitive impairments that arise as a result of seasonal allergies.

We hypothesise that exposure to pollen impairs cognitive ability and reaction time.” For the study, experts analysed 11 years of data on car crashes in the US, alongside other research about atmospheric conditions, including pollen counts.

They found there were 5.8 per cent more fatal accidents on days when the count was high, compared to when it was low.

The study, published in the Journal of Health Economics, states: “Given that driving requires high performance of both parts of the brain which deal with automated tasks and with reaction time, pollen allergies could temporarily impair drivers resulting in more traffic fatalities.

“Previous research has estimated that the cognitive impairment caused by seasonal allergies is comparable to that of being under 0.05 per cent blood-alcohol content, which is the legal driving limit in many countries.” The findings are significant as rising global temperatures driven by climate change are already causing the pollen season in the UK to become longer and more intense.

Around 10 million people in England – one in seven – have some form of pollen allergy.

Along with a runny nose, sore throat and itchy eyes, hay fever can also trigger wheezing and asthma attacks.