What thunderstorm asthma is
Thunderstorm asthma is not ordinary asthma triggered by cold air or exercise, it is an uncommon event thought to occur when high levels of grass pollen combine with a particular type of thunderstorm. Under those conditions, tiny pollen fragments can become concentrated in gusty winds near ground level, and because those particles are small enough to penetrate deep into the airways, they can trigger sudden asthma symptoms.
The critical point for hikers is that thunderstorm asthma can affect people who have never been diagnosed with asthma, so people with asthma, undiagnosed asthma, or spring hay fever are all particularly at risk.
Why it matters on trail
In urban areas, people can often move indoors quickly when conditions deteriorate. On trail, that option may not exist, because you could be several hours from your car, on an exposed ridge, or in terrain where rapid movement is difficult, so if respiratory distress develops on trail, your options narrow quickly.
Symptoms can develop and escalate rapidly too. Someone who felt completely well earlier in the day can develop wheezing, chest tightness, coughing or difficulty breathing once high pollen levels and suitable thunderstorm conditions combine.
The conditions that create the risk
Two main factors need to occur together for thunderstorm asthma risk to increase:
High grass pollen levels. In south-east Australia, the higher-risk grass pollen period generally runs from October through December. Pollen levels vary considerably from day to day depending on weather, location and seasonal conditions.
A particular type of thunderstorm. Not all thunderstorms create thunderstorm asthma conditions. Certain storms can concentrate tiny pollen fragments in strong gusty winds near ground level, increasing the amount that people breathe in.
When high grass pollen and suitable thunderstorm conditions occur together, the risk of thunderstorm asthma can increase quickly.
How forecasts and warnings work
Thunderstorm asthma forecasting is not handled through one national warning system, which is why it pays to know how your own state actually does it.
In Victoria, the Department of Health operates an epidemic thunderstorm asthma risk forecast during the grass pollen season from 1 October to 31 December. The system combines grass pollen information with weather data and forecasts, including information from the Bureau of Meteorology, and risk forecasts are published through VicEmergency as Low, Moderate or High. The forecast itself is not a formal warning, although advice and warnings may be issued through VicEmergency when risk is high.
Other states use different approaches. In NSW, for example, health authorities identify October through December as the higher-risk period, with particular risk in southern NSW and the Riverina, and some areas provide local thunderstorm asthma alert services.
Before hiking during grass pollen season, check the Bureau of Meteorology forecast for thunderstorms as well as the relevant state health, emergency and pollen information for the area you are visiting.
Who is at risk
People with asthma, undiagnosed asthma or spring hay fever are at increased risk, and people who have both asthma and hay fever, or whose asthma is poorly controlled, may face even greater risk.
Thunderstorm asthma can also affect people who have never previously been diagnosed with asthma, particularly those who experience hay fever or pollen allergies, which is exactly why it catches people off guard.
On trail, practical factors can make the consequences more serious:
- High breathing rates during sustained exertion
- Extended time outdoors during storm conditions
- Being in open or remote terrain with limited access to enclosed shelter
- Being a long distance from medical assistance
- Not having prescribed asthma medication immediately available
If you have asthma or spring hay fever, carry your prescribed reliever medication and follow your Asthma Action Plan and preventer treatment as directed. Do not leave essential medication in the car, because it is no use to you sitting in the glovebox.
Go, delay, or get off the trail
This is the decision this article is designed to help you make.
Go when pollen levels are low, no elevated thunderstorm asthma risk has been identified where forecasting is available, and thunderstorms are not expected in your area and timeframe.
Delay or modify when pollen levels are high and thunderstorms are possible. Consider shorter routes, staying closer to exit points and choosing a walk that allows you to reach enclosed shelter quickly if conditions deteriorate.
Cancel or choose an alternative when a high-risk epidemic thunderstorm asthma forecast or official warning or advice has been issued for your area, particularly if you or someone in your group has asthma or spring hay fever. If you are already on trail and high pollen conditions coincide with developing thunderstorms, move toward a safe exit or enclosed shelter while conditions still allow. Do not wait for respiratory symptoms to develop before reassessing your plan.
If symptoms develop on trail
If you or someone in your group develops sudden shortness of breath, chest tightness, wheezing or coughing during thunderstorm asthma conditions:
- Stop activity immediately and sit the person upright. Stay calm and do not leave them alone.
- If using a blue/grey reliever puffer such as Ventolin, Asmol, Airomir or Zempreon, give four separate puffs through a spacer. Give one puff into the spacer, take four breaths, then repeat until four separate puffs have been given.
- Wait four minutes. If breathing has not returned to normal, give another four separate puffs in the same way.
- If there is still no improvement, call 000 and ask for an ambulance. Continue giving four separate puffs every four minutes until emergency assistance arrives.
- Call 000 immediately if the person is not breathing, suddenly becomes worse, a reliever is unavailable, or you are unsure whether the breathing difficulty is asthma.
- If the person uses a different type of reliever medication, follow their Asthma Action Plan or the current Asthma Australia first-aid instructions for that medication.
- Do not make someone walk out if breathing is significantly compromised. Call 000, follow emergency instructions and minimise unnecessary exertion.
Thunderstorm asthma can escalate rapidly. Treat significant breathing difficulty as a medical emergency.
Key points to remember
- Thunderstorm asthma can affect people who have never been diagnosed with asthma
- People with asthma, undiagnosed asthma or spring hay fever are particularly at risk
- High grass pollen and particular thunderstorm conditions need to combine for the risk to increase
- The higher-risk grass pollen period in south-east Australia generally runs from October through December
- Thunderstorm asthma forecasting and alerts vary between jurisdictions, so check local health and emergency information as well as the weather forecast
- On trail, distance from shelter and medical assistance can make sudden breathing difficulty more serious
- Know asthma first aid and carry prescribed medication if you are at risk
None of this is complicated once the two triggers, pollen and storm type, are in your head together, which is really what the go, delay, or cancel decision above comes down to.
