By National Asthma Council Australia Director and respiratory physician Professor Peter Wark

Thunderstorm asthma refers to a specific event that occurs in spring and summer in Australia where people at risk are exposed to high levels of grass pollen during a thunderstorm and may experience an acute severe attack of asthma.

In Australia as we move into spring particularly if there have been rains during winter there is increased grass growth and pollen. In spring time as the weather changes, thunderstorms increase in frequency and develop gusts of wind that blow across the plains lifting grass pollen up into the air. The pollen reaches the moist warm air that causes the grass seeds to explode, releasing millions of pollen grains. As the storm develops cold air forces these pollens suddenly down back to the surface where they are released in very high numbers in a short period of time as the thunderstorm rolls in.

For people who have an allergy to grass pollen exposure to these pollens can excite an immediate allergic immune response. In people who experience hayfever, this leads to sneezing, red itchy eyes, itchy throat and their nose runs. In people with allergic asthma a more severe reaction may occur, the pollens enter the airways and an immune response occurs leading to worsened inflammation, a build-up of mucus and spasm of the smooth muscle that surrounds the airways. This causes chest tightness, wheeze and difficulty breathing which is of course an asthma attack.

Thunderstorm asthma events, while rare, certainly can be frightening and while fortunately they do not occur that often, the risk is always there each season. The best known of these events that had the largest effects occurred in Melbourne in November 2016. That unfortunately resulted in thousands of people presenting to hospital with acute asthma and sadly eight people lost their lives.

Exposure to grass pollen occurs every spring and worsens both asthma and hay fever in people who have grass pollen allergy. This results in an increase in symptoms, risk of asthma attacks and the need to use more asthma medications.

Thunderstorm asthma events are more likely to occur in an area surrounded by plains with grass and events in Australia have been recorded in Melbourne, Wagga Wagga, and Tamworth. However, these events could occur in any location if meteorological conditions were correct at the time. For the Illawarra that is probably less likely, as well as less likely to occur on such a large scale.

Usually exposure to pollen is in low levels and leads to symptoms of hay fever with a runny nose, itchy eyes or itchy throat. In the case of allergic asthma, someone’s asthma is more troublesome, they may be breathless when they try to exercise, they start to use their reliever medication more often, then may be waking throughout the night with a cough. These are all signs that their asthma may not be well controlled.

The best protection against thunderstorm asthma is to have good day-to-day control of your asthma. That means most people with asthma over the age of six years should be using a regular inhaled “preventer” that contains a low-dose corticosteroid. That controls the inflammation present in the airways and when the lungs are exposed to grass pollen they are less likely to experience a worsening of their asthma and severe asthma attacks.

Preventers can be used every day or in combination with a reliever on an as-needed basis. For everyone with asthma, these medications need to be prescribed and the best course of action determined in consultation with your doctor.

All people with asthma should carry a reliever (or puffer) medication with them and have a personalised asthma action plan so they know how to treat asthma when an attack occurs.

In the case of hay fever, the best treatment for those with grass pollen allergy is to start regularly using a low-dose intranasal corticosteroid preventer at the start of spring and continue it through summer. If symptoms still occur you can purchase a non-sedating antihistamine from the chemist. Your pharmacist or doctor can advise how to use both these medications and for whom they are suitable.

Asthma can be difficult to diagnose in young children. Under the age of one this is really not possible. In preschool children may develop a wheeze, especially with virus infections but not all of these children will go on to develop asthma, many growing out of this by the time they reach school. In preschool children the development of other allergies, such as eczema and hay fever, associated with recurring episodes of wheezy illnesses, especially where there is a family history of asthma, does mean that the child may go on and develop asthma later in life. By the age of six years children with frequent wheezy episodes or persistent symptoms who need to use a reliever weekly will benefit from using a regular inhaled preventer for their asthma.

For more information, visit the National Asthma Council Australia website