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Seasonal allergies are nothing new, but they’ve been worsening as the climate grows warmer. The growing season starts earlier now — in North America an average of 20 days earlier — and lasts longer, too, extending the length of time when plants are pumping pollen into the air. And the resulting misery arises not just because there’s more pollen to breathe in or because it’s around for increasingly longer seasons. At least one study has indicated that the more carbon there is in the air, the more potent the pollen itself is.

Hay fever kicks in when the immune system isn’t able to distinguish between a genuine threat (like a virus) and particles like pollen that are harmless. That’s why adults can develop seasonal allergies when they move to a new region and encounter pollens their immune system doesn’t recognize. Now, thanks to climate change, you don’t even need to move: The warmer climate is shifting growing zones northward, allowing plants to extend their natural range.