Thunderstorm Asthma: Symptoms, Risk and What to Do

What Is Thunderstorm Asthma?

Thunderstorm asthma is a sudden outbreak of asthma-like symptoms — wheezing, coughing, chest tightness and breathlessness — that follows a thunderstorm during grass pollen season. On a normal high-pollen day, grass pollen grains are too big to get past your nose and throat, which is why they cause hay fever (sneezing, a runny nose and itchy eyes) rather than breathing problems. A thunderstorm changes that.

• radio_button_uncheckedAs a storm builds, strong winds and updraughts sweep large amounts of grass pollen up into the clouds.
• radio_button_uncheckedMoisture and the storm's energy cause the pollen grains to absorb water and burst, or rupture, into hundreds of much smaller fragments.
• radio_button_uncheckedThe storm's downdraughts then carry these tiny particles back down to ground level, right where people are breathing.
• radio_button_uncheckedBecause the fragments are so small, they slip past the nose and throat and travel deep into the airways and lungs, where they can trigger a rapid asthma attack.

The trigger in Australia is overwhelmingly ryegrass (Lolium perenne) pollen — the most allergenic grass pollen in the country and the same one that drives the spring hay fever peak. This is why thunderstorm asthma is a spring and early-summer phenomenon, and why the grasslands north and west of cities like Melbourne make some regions especially high-risk.

Who Is at Risk?

The most important thing to understand about thunderstorm asthma is that you do not need a history of asthma to be affected. Many people caught out by these events have never had an asthma attack in their life. The common thread is springtime hay fever.

• radio_button_uncheckedPeople with spring hay fever (seasonal allergic rhinitis) — this is the single biggest risk group, whether or not they have ever had asthma.
• radio_button_uncheckedPeople who are allergic to ryegrass pollen in particular, which includes a large share of Australian hay fever sufferers.
• radio_button_uncheckedPeople with asthma, especially if it is not well controlled, or if it tends to flare up in spring.
• radio_button_uncheckedPeople who wheeze or feel tight in the chest after exercise or during high-pollen days, even if they have never been formally diagnosed.
• radio_button_uncheckedAnyone living in or visiting a high-risk area — inland and western parts of Victoria and other regions with extensive ryegrass pastures — during grass pollen season.

Symptoms to Watch For

Thunderstorm asthma symptoms can come on within minutes to a couple of hours after a storm passes through. They are the classic symptoms of an asthma attack, and they can range from mild to life-threatening:

• radio_button_uncheckedWheezing — a whistling sound when breathing, particularly when breathing out
• radio_button_uncheckedA persistent cough that does not settle
• radio_button_uncheckedTightness or pain in the chest
• radio_button_uncheckedShortness of breath, or feeling that you cannot get enough air
• radio_button_uncheckedDifficulty speaking in full sentences because you are too breathless
• radio_button_uncheckedIn a severe attack: gasping for air, blue or grey lips, exhaustion, or confusion — these are medical emergencies

The 2016 Melbourne Event

On 21 November 2016, Melbourne experienced the world's most severe recorded thunderstorm asthma event. A powerful storm swept through the city during peak ryegrass pollen season, rupturing pollen into fine fragments across a densely populated area. Over roughly 30 hours, ambulance services and emergency departments were overwhelmed. More than 9,500 people were affected and taken to hospital, and 10 people died — many of whom had hay fever but had never been diagnosed with asthma.

The 2016 event reshaped how Australia prepares for these storms. It showed that thunderstorm asthma can strike quickly, on a mass scale, and hit people who had no reason to think they were vulnerable. Out of it came the warning and forecasting systems now in place, particularly in Victoria.

Warning Systems: How to Stay Informed

During grass pollen season, several Australian services help you see a high-risk day coming so you can prepare in advance rather than react in the moment:

• radio_button_uncheckedEpidemic thunderstorm asthma forecasts — the Victorian Department of Health issues these during grass pollen season, rating the risk (for example low, moderate or high) region by region. Sign up for alerts at health.vic.gov.au.
• radio_button_uncheckedVicEmergency — the Victorian warnings app and website broadcasts epidemic thunderstorm asthma warnings alongside other emergency alerts, so you can get a push notification on a high-risk day.
• radio_button_uncheckedDaily pollen counts — Melbourne University's AusPollen (Melbourne Pollen Count) and similar services in other states publish daily grass pollen forecasts through the season. Weather apps such as BOM Weather and Weatherzone often include pollen data too.
• radio_button_uncheckedBureau of Meteorology (BOM) storm forecasts — checking whether thunderstorms are likely, and combining that with the pollen count, tells you when the risk is highest.

How to Prepare and Prevent It

You cannot control the weather, but you can lower your risk substantially by controlling your hay fever and having a plan for high-risk days. If you get spring hay fever, work through this checklist before pollen season starts.

Medicines and Access in Australia

Thunderstorm asthma preparation involves three different kinds of medicine, and it helps to understand what each one does and how you get it in Australia — because they sit at very different levels of access.

Asthma First Aid: The 4x4x4 Steps

If someone is having an asthma attack — sudden wheezing, coughing, chest tightness or breathlessness after a storm — use the 4x4x4 asthma first aid method endorsed by Asthma Australia. It works even if the person has never been diagnosed with asthma, and it is safe to give reliever medication while you wait for help.

Frequently Asked Questions

What are the symptoms of thunderstorm asthma?

Thunderstorm asthma causes classic asthma symptoms that come on suddenly during or after a storm in grass pollen season: wheezing, a persistent cough, chest tightness and shortness of breath. It often starts as your usual hay fever but then moves into your chest. In severe cases a person may gasp for air, be unable to speak in full sentences, or develop blue or grey lips — these are medical emergencies that need 000. If your spring symptoms suddenly affect your breathing, take it seriously.

Why does thunderstorm asthma affect Melbourne so badly?

Melbourne sits beside vast ryegrass pastures to its north and west, so it records some of the highest grass pollen counts in Australia during spring. Combine that with the city's changeable spring weather and frequent thunderstorms, and you have the exact recipe for thunderstorm asthma. That combination is why Melbourne experienced the world's most severe recorded event on 21 November 2016, when more than 9,500 people were hospitalised and 10 died. It is also why Victoria now runs a dedicated warning system.

How do I get thunderstorm asthma warnings in Victoria?

During grass pollen season the Victorian Department of Health issues epidemic thunderstorm asthma forecasts, rating the risk region by region — you can sign up for alerts at health.vic.gov.au. The VicEmergency app and website also broadcast thunderstorm asthma warnings alongside other emergency alerts, so you can get a notification on high-risk days. Checking the daily grass pollen count (for example the Melbourne Pollen Count) alongside the storm forecast gives you the fullest picture.

Can I get thunderstorm asthma if I've never had asthma?

Yes — and this is the most important thing to know. You do not need a history of asthma to be affected. The main risk factor is spring hay fever, particularly a ryegrass pollen allergy. Many people caught out in past events, including the 2016 Melbourne event, had never been diagnosed with asthma. If you sneeze and get a runny nose or itchy eyes every spring, you are in the at-risk group, and it is worth talking to your GP before the season about whether you should have a reliever inhaler on hand.

What should I do during a thunderstorm asthma warning?

If a high-risk day is forecast, stay indoors before, during and for a while after any thunderstorm, with windows and doors closed and the air conditioner set to recirculate. Keep taking your hay fever treatment, use your preventer inhaler if you have been prescribed one, and keep a reliever inhaler within reach. Avoid being outside — especially exercising or gardening — as the storm rolls in. If you develop sudden wheezing, coughing or breathlessness, start the 4x4x4 first aid steps and call 000 if there is no improvement or the attack is severe.

Can I buy a reliever inhaler without a prescription in Australia?

Yes. A salbutamol reliever inhaler (such as Ventolin or Asmol) is a Pharmacist Only (Schedule 3) medicine, so you can buy one from a pharmacy without a prescription — you just ask at the counter, and the pharmacist will check a few things first. A preventer inhaler is different: it is prescription-only and needs to be prescribed and reviewed by a GP. If you get spring hay fever and are worried about thunderstorm asthma, speak to your pharmacist or GP well before the season starts.