Red eyes just come with the territory when you and the kids are swimming in the pool, and we all assume that the culprit is just the chlorine. But a shocking—and ultra icky—new report by the Centers for Disease Control and Prevention (CDC) says there’s a little more to it than that—and it isn’t pretty.

It is the chemicals, true, but bloodshot eyes are actually caused by chlorine mixing with urine and sweat in the water, according to the CDC. Ew! Also? The stronger the chlorine smell, the more pee there is in the pool. Um. Hmm. That makes us rethink our weekend plans just a little bit, not to mention our local pool membership. How ‘bout you?

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