This allergy season has been terrible. It seems like everyone I know has been running around with leaky eyes, even those of us who aren’t typically pollen-sensitive. Granted, there was an unusual amount of tree sperm in the air this year, but it seemed strange that everybody — really, everybody! — was afflicted. But a new study by Finnish researchers explains everything: The reason we’re all so sick is that we live in the city.

According to this study, published in Proceedings of the National Academy of Sciences and based on research done in Finland, people who live in cities are more prone to developing allergies and asthma because their environments lack biodiversity. That’s not biodiversity as in “not enough kinds of cuddly wildlife” (although that too!) — it’s about the diversity of bacteria that live on your skin. If you live in the city, these freeloaders are less varied, and that spells trouble.

The study found that people living on farms or near forests had way more types of bacteria roaming around their epidermises. People living in cities had fewer. In particular, city-dwellers lacked one gammaproteobacterium that helps humans not get totally snotty and gross when they encounter pollen.

So even though there are fewer trees around in cities to smear pollen all over humans, there are also fewer bacteria around to keep our bodies from freaking out when it happens. Perhaps this is why everyone I know in New York City has been miserable for the past few months. We need to get out to the forest and cozy up to some new, strange microbes.

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