In spring and summer most of us like to spend plenty of time outdoors. However, for many people with asthma, the high pollen levels in the air at those times of the year can bring on asthma symptoms.
Pollen is the mass of tiny grains produced by a plant for the purpose of fertilisation. Some brightly coloured plants such as wattles have a small amount of relatively heavy, sticky pollen that is spread by birds or insects. Other plants such as weeds, grasses and various trees have smoother, lighter pollen and lots of it. These plants use the wind to spread their pollen, and it is this type of pollen that is a problem for many people with asthma.
Pollen is a common trigger of asthma and produces its effect by means of an allergy. Pollen is thus known as an ‘allergen’, which is an essentially harmless substance that sparks off an abnormal (‘allergic’) reaction in susceptible people. In the case of asthma, the lungs are affected, bringing on the typical asthma symptoms of wheeze, cough, chest tightness and difficulty in breathing.
Your allergy to pollen can mean you may also get the symptoms of hay fever (so-called ‘seasonal allergic rhinitis’) — watery and itchy eyes, sneezing, runny or blocked nose, and itchy ears, mouth and throat — which may also benefit from treatment.
Pollen causes more of an impact in Australia during summer than at other times of the year. However, in the warm northern regions of Australia, grass pollens can cause problems all year round for people with asthma.
The pollen season occurs when plants and trees have flowers. Some plants will shed large amounts of pollen in the early spring, for example, introduced, European street trees such as the London plane; others will shed throughout spring and summer, for example, grasses such as ryegrass and the weed Paterson’s curse; while others can be a problem for most of the year, for example, she-oaks (native pine trees) and the weed plantain.
Intact pollen grains carried by the wind may irritate your nose and sinuses to cause hay fever symptoms. However, when the air is humid or it rains, the pollen grains absorb moisture from the air and break apart to release tiny starch granules. These particles are allergens and are small enough to be breathed into the small airways of your lungs, and can bring on asthma symptoms. ‘Thunderstorm asthma’ is a term used to describe the rise in the number of people with asthma symptoms around the time of a thunderstorm.
It is also thought that these broken-up pollen grains stick to the exhaust particles from diesel engines, to create particles that are more easily breathed into the lungs.
So high levels of pollen in the air, as occur in the spring and summer, rain, and high levels of exhaust fumes can mean a high-risk day for people who have pollen-induced asthma.
In the warmer months, most television weather forecasts include a pollen count for the day that is based on the average number of pollen grains measured per cubic metre of air. Pollen count may be described as low, medium, high or extreme.
Most of the plants that cause pollen-induced asthma in Australia are introduced species and include:
The pollen of some native species, such as native pine trees (she-oaks) and white Cypress pine, can also trigger asthma symptoms.
If your asthma seems to be triggered by pollen, you can try the following measures to reduce your pollen exposure; however, research has not yet shown whether this approach effectively controls asthma symptoms.
Several strategies that don’t involve avoiding pollen may also be helpful.
Last Reviewed: 03 September 2007