Pollen isn’t infectious and doesn’t cause disease the way that bacteria and viruses do. Instead, some people develop an allergy to the pollen of certain plants and have symptoms when that pollen is around in the environment. That is, for these people a particular type of pollen is an allergy trigger.

Whole pollen grains landing in the eyes or nasal passages can trigger rhinitis or hay fever, characterized by a blocked or runny nose, sneezing and itchy eyes. Around 18% of Australians have hay fever.

Pollen can also fragment into bits small enough to enter the lungs and trigger asthma in a sensitive person. Asthma causes a narrowing of the airways making it harder to breathe. Around 1 in 9 Australians have asthma.