Those red eyes you get from swimming aren't caused by chlorine, according to an official with the Centers for Disease Control and Prevention. And the substances in the pool that do cause your bloodshot eyes will probably make you a little seasick. “Chlorine binds with all the things it’s trying to kill from your bodies, and it forms these chemical irritants. That’s what’s stinging your eyes. It’s the chlorine binding to the urine and sweat,” says the appropriately named Dr. Michael J. Beach, associate director of the CDC's Healthy Water program.