Low pollen count, real symptoms — why allergy forecasts miss some people

October is spring. Grass pollen season is beginning across southern Australia — Melbourne, Canberra, Adelaide, the regional south-east — and over the next eight weeks many people with hay fever will be watching a number on a phone screen to decide whether to take a tablet, carry a tissue, or cancel a morning walk.

The problem with that number is that it reflects the population average. For some people it is a reasonable guide. For a meaningful proportion it is not, and a new study helps explain why.

Research from the University of Queensland, published in a Wiley/AGU journal and reported by RACGP newsGP, draws on around 115,000 symptom reports from approximately 25,000 users of the Melbourne Pollen app over 2017 to 2023. The central finding: people differ substantially in their sensitivity to grass pollen. Some participants reported significant symptoms on days classified as low-pollen. Others reported little or no impact on days classified as high. A population-level pollen count, useful as a general signal, is not a reliable individual predictor.

Two additional factors complicate the picture: fine particle air pollution was independently associated with allergy symptoms, and non-grass airborne pollens also drove symptom reports on days when grass pollen alone would not have explained the response.

What the demographics of app users reveal

The study carries a useful demographic footnote. App users aged 31 to 50 made up 47% of participants — roughly double their share of the Greater Melbourne population at 29%. This over-representation of midlife adults, particularly in the age band that aligns with a heavy professional and family load, suggests allergy burden is most felt — and most tracked — by people in this cohort. Meanwhile, those aged 61 and over were under-represented: 8% of app users despite comprising 19% of the population, likely reflecting lower app adoption in older adults. The researchers flag this as demographic selection bias and a reason to actively encourage older patients with allergies to use digital tracking tools.

Hay fever now affects nearly one in four Australians, according to AIHW data — up from 19% in 2017–18 to 24% by 2022. That is not a trivial public health figure. For a condition that is frequently under-treated on the basis that it is “only hay fever,” the rising prevalence sits alongside growing evidence that poorly controlled allergic rhinitis impairs sleep, concentration, and productivity, and that in people with comorbid asthma it increases the risk of exacerbations.

Both-and: population forecasts and individual risk

Pollen forecasts are valuable. They help people plan outdoor activities, time preventative medication, and understand seasonal patterns. A “high” day is a reasonable signal for most people to be more careful. The Melbourne Pollen app and apps like AirRater extend the utility of these forecasts by adding air quality layers and allowing symptom tracking alongside count data.

And: for people whose sensitivity sits at the higher end of individual variation — and this study quantifies that the range is wide — forecasts calibrated to the average may consistently under-warn. A person who reliably becomes symptomatic at pollen concentrations that register as “low” needs a plan that does not wait for the forecast to reach “high.”

Dr Nick Cooling, Chair of RACGP Specific Interests Allergy, identifies higher-risk groups: people with asthma, a history of past severe or extreme symptoms, significant prior reliever medication use, or allergic conjunctivitis alongside rhinitis. Melbourne’s thunderstorm asthma events — the most recent major event in 2016 resulted in the largest mass casualty event in Victorian history from a respiratory cause — demonstrate the consequence of assuming hay fever is a minor condition. The specific mechanism of thunderstorm asthma involves grass pollen rupturing in moisture and releasing sub-pollen particles that penetrate deeply into the airways; the events tend to occur in spring, under conditions that look nothing like a stereotypical “high pollen day” on a standard forecast.

2 cents

If you have hay fever and it is not well controlled — affecting sleep, work, or activities — October is the right time for a GP appointment, not when you are in the middle of a bad week. A personalised management plan, an accurate medication regime (many people under-dose antihistamines or use them irregularly), and clarity about whether your symptoms warrant referral to an allergist are all worth establishing before peak season.

If you have hay fever and asthma together, a written asthma action plan that accounts for pollen season is not optional. Both conditions share inflammatory pathways, and the co-existence of the two increases your risk meaningfully during high-pollen events.

Tracking your own symptoms alongside a pollen app for a few weeks at the start of the season can give you and your GP a clearer read on your personal trigger threshold — more useful than a population forecast alone.

Verdict: yes — the finding that individual pollen sensitivity varies substantially is clinically important, particularly for patients with asthma and those who have learned not to trust their own symptoms against a “low” forecast.

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Sources cited

1. Low pollen not always low risk — RACGP newsGP
2. Personalised pollen risk forecasting — AGU/Wiley
3. Allergic rhinitis (hay fever) in Australia — AIHW