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Scientists Say It's Not Chlorine In Pools That Makes Your Eyes Red... It's Pee

The U.S. Centre for Disease Control says urine and sweat in public pools reacts with chlorine and causes eye irritation.

Here's an excellent reason to wear your goggles at the local pool: Researchers at the Centre for Disease Control say nitrogen compounds in urine and sweat react with chlorine to form an irritant that can sting your eyes and turn them red.

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An article published by the CDC in June says chlorine binds with urine and other waste from humans to create irritants known as chloramines.

So if you thought it was chlorine just doing its job that was making your eyes red, think again.

“It’s quite the opposite,” Dr Michael Beach, associate director of the CDC's Healthy Water program told Women's Health magazine.

“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 the sweat.”

And if you've ever found yourself coughing at an indoor pool, the researchers say that's also caused by that pee-chlorine combo.

Nikitabuida / Getty Images

The problem can be particularly bad in indoor pools, if there isn't adequate ventilation.

Breathing air loaded with irritants can cause coughing, wheezing or aggravated asthma, according to the CDC.

"The symptoms of irritant exposure in the air can range from mild symptoms, such as coughing, to severe symptoms, such as wheezing or aggravating asthma. It is also known that routine breathing of irritants may increase sensitivity to other types of irritants such as fungi and bacteria," the report says.

And that strong chlorine smell at indoor pools? It's caused by too many chloramines in the air, and is actually a sign that the pool could do with more chlorine.

And they're busting another myth too: There's no such thing as a special pool dye that makes the water change colour when you pee.


“That dye is a complete myth,” says Beach. “It’s about scaring people into not urinating in the pool.”

Making sure there is enough fresh air circulating and adding more chlorine to the water can help the problem. But obviously the most effective way to stop people getting sick is by not peeing in the water in the first place and taking a shower before getting in the pool.

In Australia, the NSW Department of Health has a similiar warning about chloramines in indoor swimming pools:

"Chloramines are poor disinfectants and greatly reduce the disinfection power of free chlorine, irritate mucous membranes, cause eye stinging and red eyes, and irritate respiratory systems." the department says on its website.

"Pool operators should limit the amount of ammonia entering the pool by encouraging swimmers to use the toilet and to shower with soap before entering the pool."

Happy swimming!!

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