Getting red, stingy eyes after swimming is not because of the chlorine in the pool – it is urine.

Michael J Beach, associate director of the Centers for Disease Control's Healthy Water programme, told Women's Health chlorine has been given a bad reputation when it comes to swimming and eye irritation.

Instead of causing the stinging redness, the chlorine is trying to kill off bodily fluids emitted in the pool and this causes a chemical reaction that leads to irritation and coughing.

"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," he said.

On the CDC healthy swimming advice page, experts note that the chemicals react when chlorine binds with sweat, urine and other waste, they move from the water to the air. Breathing in this air can lead to coughing, wheezing or aggravating asthma.

red eyes swimming
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"Getting swimmers to shower before getting in the pool and promoting regular bathroom use to reduce the amount of urine in the pool will decrease the formation of irritants," the website said.

Beach also said there has been an increase in disease outbreaks at public swimming pools in recent years because of adults and children entering the water when they have diarrhoea.

"We have a new parasitic germ that has emerged that's immune to chlorine," he said. "We've got to keep it out of the pool in the first place. We need additional barriers.

"If you're swimming next to someone who has diarrhoea, there's no protection."

Beach's comments followed a partnership between the CDC, the Water Quality and Health Council and the National Swimming Pool Foundation for the Healthy Swimming Programme.

They are aiming to educate people about the dangers of pools and what people can do to stay safe: "We think that swimming is a really fantastic activity," Beach said. "We want to keep it that way."