Australia got the arse end of the stick when it comes to seasonal allergies, we're definitely mixing it up with the big boys in the global sneezing stakes (ISAAC study, 1998):
Another article has worked out that: "Australia has a high prevalence of atopic disorders, ranking among the highest in the world". Oh, fab. We also know that atopy is increasing across the world, but that it appears to be a disease that is particularly a scourge of developed nations.
Nonetheless, it doesn't stop articles like this popping up every now and again:
Global Warming May Worsen Hayfever
Global warming could bring more hay fever, according to government research that shows ragweed produces significantly more pollen as carbon dioxide increases.
Now kids, can anyone spot the non-sequitur in that?
I will concede that CO2 fertilisation could crank up the pollen output, its plant food, after all, but buried in this is the logical fallacy that carbon dioxide levels are synonymous with global warming, ergo global warming is causing an increase in hayfever.
Another, more important issue is that rising pollen levels will only cause misery for those people who are already atopic, and increasing atopy in industrialised nations is far more likely to be attributable to such factors as the hygiene hypothesis. (In a nutshell, that early exposure to microbial infection at critical points in development helps to shift our immune system towards producing chemicals that are less likely to cause the inflammatory reactions of atopy. Wow, I can't believe I got that down to one sentence.)
So if you ever needed an excuse to explain why your children are in the backyard eating dirt mixed with possum poo, you now have a fairly compelling one. Additionally, CO2 fertilisation affects all plants, not just that pain-in-the-arse ragweed and rye grass, so there is an upside to this, somewhere, I just can't think of it right now because my head is exploding.