Hay fever can strike even when grass pollen concentrations are low

A low pollen count does not always mean a symptom-free day for those with asthma or hay fever, with new research showing some people still experience symptoms even when grass pollen levels are classified as low.

University of Queensland researchers analysed nearly 115,000 symptom reports from 25,000 Melbourne Pollen app users between 2017-2023, and compared how environmental factors like pollen concentrations, weather and air pollution influenced the way people reported their hay fever symptoms.

Epidemiologist and UQ PhD candidate Max Tyler said the findings reinforced differences in people’s sensitivity to pollen.

“We found measurable increases in symptoms for some people on days when grass pollen levels were classified as low,” he said.

"People vary considerably in how sensitive they are to grass pollen, but grass pollen wasn't the only factor linked with how people reported their symptoms.

"Other airborne pollens and fine particle air pollution were also associated with reported symptoms.”

“So, 2 people can be exposed to the same amount of grass pollen but experience very different symptoms.”

Senior author Associate Professor Nicholas Osborne from UQ’s School of Public Health said the findings show that once exposed to pollen, the onset of symptoms can be rapid.

"When someone with asthma or allergies is exposed to pollen, they will likely be feeling the effects within 30 minutes because of their hypersensitivity,” Dr Osborne said.

“Overall, symptoms were strongest on the day of exposure and generally less severe the next day.”

Researchers also found adults under the age of 40 generally reported more symptoms following grass pollen exposure than older age groups, although differences in how people interacted with the app may have influenced the finding.

Mr Tyler said the findings could help inform clearer public health messaging and future approaches to personalised forecasting.

“There is an opportunity to build upon existing pollen forecasts by combining a person's allergy history and symptom patterns to estimate their individual symptom risk,’’ he said.

“The aim is to give people more useful context, helping them make informed decisions about whether to take preventative medication or modify outdoor activities.”

Read the research in GeoHealth.