Why Melbourne is the hayfever capital of the world

An Amazon rainforest study has shed light on the causes of urban hayfever — and revealed why so many people in Melbourne suffer.

An Amazon rainforest study has shed light on why Melbourne is the hayfever capital of the world.

When greater Melbourne’s pollen count hits 50 grains per cubic-metre, expected to occur in late October, the city’s hayfever season formally kicks off.

But many may be suffering symptoms already.

“We are the capital of the world for allergies, for hayfever … at least one in three people in greater Melbourne suffer from it,” study co-author, La Trobe University’s Dr Philip Taylor, said.

Melbourne’s notoriously changeable weather, together with introduced grasses and vegetation, particularly birches and plane trees, result in the city suffering the highest allergic reactions anywhere.

Now, a five-year study, carried out using the 300-metre-high Amazon Tall Tower Observatory in Brazil, has shed new light on pollen air travel and the causes of urban hayfever.

A five-year study has shed new light on pollen air travel and the causes of urban hayfever. Picture: Tony Gough

Tracking the height and travel distance of hay fever-causing particles such as ­pollen and fungi in the pristine atmosphere above the Amazon, scientists found that pollen generally does not achieve the height required for long-range dispersal. “We found that, rather than rising high into the air and scattering over large distances, pollen actually travels fairly low to the ground,” Dr Taylor said.

“City dwellers often blame the country for their hay fever symptoms, even as farmland grows more distant.

“But biophysics tells us that the cause must be much closer to home,” he said.

Rye grasses in suburban lawns and nature strips and sports fields, together with ­European trees and fungi, are the main contributors to urban hay fever.

“We now know that pollen can’t travel very far, which suggests that our urban streets and suburban backyards are more likely to blame for the symptoms,” he said.

Councils mowing reserves more frequently and greater use of native plants and trees can help reduce hay fever, but Dr Taylor said our frequently changing weather ­increased pollen dispersal.

“Melbourne’s ‘four seasons in one day’ instability leads to pollen being fragmented and causing more allergic reactions,” Dr Taylor said.

The study is published in the journal Nature – Climate and Atmospheric Science.

The study is published in Nature – Climate and Atmospheric Science.