Thunderstorm asthma: what is it, what should you do?

By Ewan McDonald

Thunderstorm asthma: what is it, what should you do?
Until this week, few people knew thunderstorms could trigger fatal asthma attacks in people who’d never had the condition. What is it, what should you do?

When a storm hit Melbourne on Monday night, hundreds of people suffered attacks of “thunderstorm asthma”. Many had never experienced asthma before. What is thunderstorm asthma, and what should you do if it strikes you or someone around you?

Two people are known to have died – Hope Carnevali, a 20-year-old law student, who died on the front lawn of her home before an overloaded ambulance service could respond to her family’s calls, and Omar Moujalled, an 18-year-old high school student, who died at a doctor’s surgery.

More than 1900 calls were logged by the emergency services, which simply ran out of ambulances to dispatch.


Thunderstorms can trigger respiratory problems by causing particles of pollen that are normally too big to enter the airways to explode.

“Thunderstorm asthma is triggered when there is a sudden change in weather conditions,” explains Dr Simon Judkins of the Australasian College for Emergency Medicine.

“The movement from a hot a windy day where there is an increased pollen load in the air to an incoming storm front which adds a lot of moisture to the air will see pollens absorb the moisture, and burst.

“This releases thousands of tiny allergen particles which are then inhaled by people and can trigger asthma attacks.”

In Melbourne, this phenomenon occurs when moisture-charged winds immediately before a storm whip up rye grass pollen from the pastures north and west of town, sweeping them into the city. Rye grass is the pollen that causes most cases of hay fever in Melbourne.

“Melbourne, being surrounded by parks and bushland, combined with the well-recognised Melbourne ‘four seasons in one day’ weather patterns is particularly set up for this scenario,” said Judkins.

A high pollen-count day is one with 50 grass pollen grains per cubic metre of air, averaged over 24 hours. Extreme days have 100-plus grass pollen grains per cubic metre of air. On Monday, the pollen count hit 102 grass grains per m3 of air recorded.


People with asthma and other allergy syndromes will be affected but children and the elderly are very vulnerable

According to the Australasian Society of Clinical Immunology, around one in four people with allergic rhinitis (hay fever) also have asthma.

Some people with severe allergic rhinitis (hay fever) think that their allergic rhinitis turns into asthma or will make them tight in the chest or wheeze. This is incorrect as pollen can trigger asthma as well as allergic rhinitis symptoms. 

So can people without asthma suffer from “thunderstorm asthma”?

Not everyone who gets thunderstorm asthma has had it before. They have normally had severe pollen allergic rhinitis (hay fever) and most have been found to be allergic to ryegrass. Presumably the massive load of small allergenic particles being inhaled straight into the lung trigger these attacks. 

Dr Judkins: “So many people, for example, will have hay fever, which is an allergy to pollens, but may not have had asthma symptoms. However, in these circumstances, when they are exposed to such a large allergen load which is deposited into their lungs, they will have an asthma attack.”


Inhaling the pollen fragments can cause an allergic reaction in the lungs resulting in the sudden onset of symptoms such as shortness of breath, a cough, a wheeze, and chest tightness. 

Thunderstorm asthma feels like your lungs have “tightened up”, says Judkins.  “If you have seen anyone who has had an allergy and their lips or eyes swell, a similar thing happens in the lungs. The patient gets ‘bronchospasm’ and swelling, which makes it harder to breathe in and out.

“Think of how you feel when you try to breathe in and out through a straw. It’s very hard work, very tiring and distressing.”

The best way to treat thunderstorm asthma is to prevent it occurring, where possible. So good asthma control is essential.


Get help. While some sufferers will have asthma medications with them and will recognise the symptoms and start implementing their asthma plan, this may be a first-time experience for many people. Ventolin spray is the first-line therapy, followed by steroid medication.

Your GP has these medications but, if it is outside their working hours, you may need to head to your nearest emergency department.



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