Low Pollen Count, High Allergy Symptoms? New Research Explains the Disconnect

If you check the pollen forecast before heading outside, a new study suggests the number on your screen may not tell the whole story. Researchers found that some people with hay fever still had symptoms on days when grass pollen was classified as low.

The study, published in the journal GeoHealth, was led by researchers at the University of Queensland in Australia. They analyzed nearly 115,000 symptom reports submitted by about 25,000 users of the Melbourne Pollen app between 2017 and 2023. They then compared those reports with pollen concentrations, weather and air pollution levels to see what was linked to how people felt.

The research focused on grass pollen during Australia’s spring season. Its central finding applies to anyone who relies on pollen counts, including Americans managing ragweed and other fall allergies right now.

Two people, same pollen, different reactions

The researchers found that people vary widely in how sensitive they are to pollen. Max Tyler, an epidemiologist and doctoral candidate at the University of Queensland and the study’s lead author, said two people exposed to the same amount of grass pollen can “experience very different symptoms.”

Grass pollen also wasn’t the only factor. Other airborne pollens and fine particle air pollution were associated with the symptoms people reported. A day with low grass pollen could still be a difficult day if other triggers were in the air.

Symptoms can start fast and fade by the next day

Once someone with allergies or asthma is exposed to pollen, symptoms can begin quickly. According to senior author Nicholas Osborne, an associate professor at the University of Queensland’s School of Public Health, people with these conditions will likely feel the effects within about 30 minutes because of their hypersensitivity.

Symptoms were strongest on the day of exposure and generally less severe the following day. The researchers looked at symptom patterns over the seven days after exposure.

Asthma may increase the risk of severe symptoms

People with asthma appeared to have longer-lasting risk of severe hay fever symptoms than people without asthma. Medication use was common in this group. Among the 3,915 severe symptom reports from people with asthma, 88% also noted that they had taken medication such as antihistamines, decongestants, corticosteroids or immunotherapy to manage symptoms.

The researchers also found that adults younger than 40 generally reported more symptoms after grass pollen exposure than older adults. They cautioned that differences in how age groups used the app may have influenced this result.

Limits of app-based data

Because the data came from people who chose to log symptoms in an app, the study relied on self-reports rather than clinical exams. It also focused on grass pollen in one Australian city, and the pollen thresholds used in Melbourne differ from those used in U.S. forecasts.

Moving toward personalized forecasts

The researchers said their findings point to a more individualized approach. Tyler said pollen forecasts could be improved by combining them with a person’s allergy history and symptom patterns to estimate individual risk. The goal is to help people decide when to take preventive medication or adjust outdoor plans.

Until those tools exist, the study offers a practical reminder. A low pollen count is useful information, but it isn’t a guarantee. People with seasonal allergies, especially those who also have asthma, may benefit from tracking their own symptom patterns and talking with a health care provider about when to start or adjust treatment.