Why Do Pools Make Your Eyes Red?

A long day at the pool can be hard on the eyes. When you emerge from the water after a few hours, your eyes tend to sting and might even be bloodshot. Unfortunately, that’s not a side effect of chlorine. Nope, it’s grosser. It's what happens when chlorine mixes with all the nasty stuff that comes out of people’s bodies in the pool. 

 "The nitrogen in the urine combines with the chlorine and it forms what's known as chloramine and it's actually chloramine that causes the red eyes,” Michele Hlavsa of the CDC’s healthy swimming program told Today. “It's not the chlorine itself. It's chlorine mixed with poop and sweat and a lot of other things we bring into the water with us."

This tidbit of summer-ruining information is tucked inside the CDC’s healthy swimming pamphlet [PDF]. “What you smell are actually chemicals that form when chlorine mixes with pee, poop, sweat, and dirt from swimmers’ bodies,” it says. “These chemicals—not chlorine—can cause your eyes to get red and sting, make your nose run, and make you cough. Healthy pools, waterparks, hot tubs, splash pads, and spray parks don’t have a strong chemical smell.” It also notes that swim diapers don’t keep germs from getting into the water. 

Welp. Nowhere is safe. We’re all swimming in pee. Or worse. Have a good summer!