CDC: Red Eyes after Swimming is Thanks to Pee in the Pool AGGGHHH GROSS

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The United States Centers for Disease Control, or CDC, has released its annual healthy swimming report, and hold on to your butts…literally…because they’ve revealed that the strong pool smell you associate with chlorine is actually the smell of pee in the pool. Ditto those red, irritated eyes you blame on the chemical. Oh boy.

The headlines here surprised me, because I was lucky enough to grow up with a pool that I was in constantly from the day it opened in the spring until my parents dragged me out to go to school in the fall. And I remember that the smell was stronger and my eyes more irritated just after my dad “shocked” the pool with chemicals. And, as the primary occupant of the pool, I never peed in it once. Really. Somehow my parents were able to ingrain the “no pee in the pool” rule so deeply that to this day I can’t even force myself to pee in the ocean. It’s a serious psychological handicap.

Well, the reason for all of this to be true is that the strong smell and irritated eyes do have something to do with chlorine: they come from the chlorine binding with the nitrogen in your urine to create chloramine, which is a derivative of ammonia.

And nitrogen isn’t just in your pee and poo — it’s also in your sweat and in dirt, which is where the smell came from in my pool considering that I would preface a refreshing swim with a lot of running around in the woods.

The problem is that when the chlorine is busy binding to all that nitrogen, there’s not much left over for doing what it’s really there to do: fight germs like cryptosporidium and E. coli. That can lead to serious illness if you happen to get any of that nasty water in your mouth.

So, the CDC recommends that you avoid any pool or waterpark that smells too strongly of what you think of as chlorine, since that means that there’s a large amount of grossness in there. Of course, if you’re looking for a clean waterpark, you’re probably better off just wearing a full old timey diving suit. Of course, considering that the purpose of most theme parks is to thrill and scare you, maybe knowing the risk will make it that much better! A log flume is scary, but a log flume where you might drink some poop and then spend three days on the toilet praying for death is downright terrifying.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky

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  1. Those old-timey diving suits were actually worse for hygiene. Often the materials would clog the filters. Obviously, today’s synthetic fibers work better for that.

    And yeah, you need to take a shower before and after swimming.

  2. I’d be curious to know exactly how much urine in say, a 70,000 gallon swimming pool would be needed to produce the irritating effect.

  3. OK, so I’ve only got your video to go on, but I’m still a bit confused. Chlorine smells. Pop the seal on a new bottle of bleach: same smell as a pool. Like you, I had a pool as a kid and I never peed in it. But it smelled before I got in. It smelled more when new chemicals had just been added. Open the container of chlorine tablets – same smell. There’s a fountain near where I work that kids play in, so it’s chlorinated. When there are no kids around, just fresh, chlorinated water bubbling up – it smells. I’m pretty sure I’m smelling chlorine. If it’s not chlorine and is a byproduct of the chlorine reacting, then it seems pretty clear the chlorine is reacting to create the smell as soon as it hits air or water. Maybe the CDC and I are smelling different smells? By all means, let’s shower before we swim, and let’s all agree that pools should not be peed in, much less pooped in, but I’m not buying the notion that if everyone showered and no one peed or pooped we’d suddenly have odorless pools and no eye irritation after swimming.

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