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With the Australian spring comes seasonal allergic rhinitis, or hay fever. But why do humans have a physiological response to pollen and dust? I can鈥檛 see any benefit to suffering from sore eyes, a scratchy throat and nasal congestion. So why does it occur?

Wendy Akers, Canberra, Australia

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This article appeared in print under the headline 鈥淗ay fever fever鈥�