What happens
Pollen grains are normally too big to get deep into your lungs. In a thunderstorm, strong updrafts carry pollen up into the cloud, where it soaks up water and bursts into much smaller pieces. Cold downdrafts and gusts at the front of the storm then carry these pieces back down to ground level, where people breathe them in.
The result can be a sudden asthma attack, often within an hour of the storm arriving.
Who is at risk
- People with asthma, especially if it is not well controlled.
- People with hay fever, including those who have never been told they have asthma.
- People who are outdoors when the storm front arrives.
Where it has happened
The best-known event was in Melbourne in November 2016, when thousands of people needed hospital care in a few hours. Smaller events have been recorded in Britain. In Ireland the risk is highest in June and July, when grass pollen is high and summer storms are most common.
How to stay safe
- If you have asthma, take your preventer inhaler as prescribed through the pollen season.
- Carry your reliever inhaler on High pollen days.
- When a storm is forecast on a High pollen day, be indoors with windows and doors closed before it arrives, and stay in until it has passed.
- If you have hay fever and ever wheeze or feel tight in the chest, talk to your GP before the season.
In an emergency
If someone is very breathless, can’t finish a sentence, or their reliever isn’t helping, call 112 or 999.
How pollen.ie warns you
When our forecast shows storms on a day with Moderate pollen or higher, county and town pages show a thunderstorm asthma warning with the expected time. Phone alerts include the warning too.
Questions
Has thunderstorm asthma happened in Ireland?
Large events like Melbourne in 2016 have not been recorded in Ireland, but the conditions that cause it do happen here in early summer. It is sensible to take care on stormy High pollen days.
Can you get thunderstorm asthma without having asthma?
Yes. Many people affected in Melbourne had hay fever but had never been diagnosed with asthma.
When is the risk highest?
In the first half hour or so after a storm’s gust front arrives, on days with High grass pollen. In Ireland that is mostly June and July.
This is general information, not medical advice. If you are worried about symptoms, talk to your pharmacist or GP.