Frequently asked questions

Pollen is the fine, powdery substance released by anthers, a part of the flower. Pollen grains contain the male gametes of plants, which makes male sperm the closest analogous type of cell to pollen in the human body.

Although benign, pollen from certain plants can trigger allergic diseases in sensitive individuals.

Whole pollen grains landing in the eyes or nasal passages can trigger seasonal allergic rhinitis (hay fever), characterised by a blocked or runny nose, sneezing and itchy eyes. Allergic rhinitis affects around 18% (nearly 1 in 5) of people in Australia and New Zealand (see https://www.allergy.org.au/patients/allergic-rhinitis-hay-fever-and-sinusitis/pollen-allergy).

It is important to recognize that pollen can trigger asthma as well as hay fever symptoms; around 1 in 4 people with hay fever also have asthma (see https://www.allergy.org.au/patients/asthma-and-allergy/thunderstorm-asthma). Many people with hay fever due to grass pollen allergy can get wheeze or chest tightness in the spring and summer season when they also have hay fever. This is likely to be asthma triggered by grass pollen allergy.

Counting the levels of pollen in the air means that people who have asthma (triggered by pollen) and hay fever, can be informed of days that are forecast to have high pollen levels. This information allows them to take preventative measures such as staying indoors or having their medication close at hand. Because rye grass pollen is the major allergic pollen type in Victoria, the Victorian Thunderstorm Asthma Pollen Surveillance (VicTAPS) network counts and forecasts are for grass pollen.

During grass pollen season people may notice an increase in asthma and hay fever symptoms. Grass pollen season (October through December) also brings the chance of thunderstorm asthma.

Thunderstorm asthma is thought to be triggered by a unique combination of high amounts of grass pollen in the air and a certain type of thunderstorm. For people who have asthma or hay fever this can trigger severe asthma symptoms (see Better Health Channel: https://www.betterhealth.vic.gov.au/campaigns/thunderstorm-asthma).

When a large number of people develop asthma symptoms over a short period of time, related to high grass pollen and a certain type of thunderstorm, it is known as epidemic thunderstorm asthma.

An air-sampling device called a Burkard spore trap is used to capture airborne pollen on a glass slide, which is stained with a dye and counted using a microscope.

During the grass pollen season, a slide is removed from the trap at the same time each day and counted twice. The first time all types of pollen on the slide is counted and the second time just the grass pollen (which has a distinctive shape) is counted. The daily pollen count is a report of both grass and all kinds of pollen (as grains per cubic metre of air) caught in the trap in the previous 24 hours.

There are currently eight pollen counting sites in the Victorian Thunderstorm Asthma Pollen Surveillance (VicTAPS) network. The University of Melbourne operates an inner Melbourne site at its Parkville campus and on its rural Creswick and Dookie campuses. The University of Melbourne also operates sites on La Trobe University's Bendigo campus, Federation University's Churchill campus, and at the Western District Health Service in Hamilton. Deakin University operates pollen count sites at its Geelong and Burwood campuses.

Prior to the 2017 grass pollen season there were three pollen traps operating in Victoria - in Parkville, Burwood and Waurn Ponds (Geelong).

The Victorian government has provided additional investment to expand the pollen monitoring network in Victoria by adding five pollen traps at the following locations:

• Hamilton
• Creswick (near Ballarat)
• Bendigo
• Dookie (near Shepparton)
• Churchill (near Morwell)

Eight pollen traps across Victoria will be operating and supporting the verification and refinement of the epidemic thunderstorm asthma forecasting model, by providing a more detailed understanding of pollen levels and the spread/movement of pollen across the state.

The new pollen trap locations were chosen based on a range of factors including levels of rye grass, expected wind directions and likely distribution patterns of pollen, historical peaks in asthma presentations to emergency departments, population size, and the availability of appropriate locations to house, operate, maintain and staff daily pollen counts seven days a week from 1 October to 31 December.

The daily grass pollen count for Victorian sites is available on this website, https://www.melbournepollen.com.au and on the Melbourne Pollen Count App.

Research shows that grass pollen is by far the most common cause of hay fever in Victoria.

Plants release their pollen when they are flowering, and different types of plants flower at different times of year. Many deciduous trees such as birch, plane and elm flower in late winter and early spring, for example, whereas many grasses flower in the period from October to December.

Grass pollen data collected in Melbourne for more than 20 years shows that the highest levels start occurring, on average, in mid-October and fluctuate daily until the end of December. By the end of November grasses start dying off and the levels of grass pollen in the air begin to reduce. The exact start and finish of grass pollen season varies slightly from season to season, but is typically from 1 October to the end of December.

A number of factors affect the daily count, including daily fluctuations in temperature, wind conditions, humidity and precipitation, and of course the biology of the grasses themselves.

Most grasses flower in late spring and early summer. During the flowering season, weather conditions such as wind and humidity will also affect how much grass pollen is in the air.

For example, Melbourne's worst grass pollen days are in November, when hot northerly winds bring pollen into the city from pastures in the surrounding countryside. Southerly winds, by contrast, are cooler and more humid and bring mainly pollen-free air into Melbourne from the ocean.

Pollen forecasts simply reflect the expected amount of pollen in the air. They can help people with hay fever (seasonal allergic rhinitis) who may choose to avoid being outdoors on these days. In Victoria grass pollen seems to be the most problematic.

Epidemic thunderstorm asthma forecasts combine grass pollen forecasts with the prediction of a certain type of thunderstorm thought to produce a thunderstorm asthma event.

More information about thunderstorm asthma is available on the Better Health Channel https://www.betterhealth.vic.gov.au/thunderstormasthma

Media enquiries about the Epidemic Thunderstorm Asthma Forecasting Service should be directed to the Victorian Department of Health and Human Services on 1300 761 874.

The Epidemic Thunderstorm Asthma forecasting service will run from 1 October until 31 December, the typical Victorian grass pollen season. To access the epidemic thunderstorm asthma forecasts, download the Vic Emergency App or visit emergency.vic.gov.au/prepare