Red eyes are something most swimmers have experienced in a pool.

However, although it is usually based on the amount of chlorine in the water, researchers have warned the reality is far less appealing.

They say the real cause is urine in the pool.

Researchers say the red eyes are caused by urine in swimming pools, not chlorine - and have launched a campaign to stamp it out.

THE COLOUR CHANGE MYTH It's the most common pool myth of all time: If you pee in the pool, the water will change color and everyone will know. Parents have long used the story of a chemical that changes color in the presence of pee to keep their children from peeing in the pool. The fact is there is no such dye that currently exists, researchers say. Advertisement

Health experts from the U.S. Centers for Disease Control and Prevention (CDC), the Water Quality and Health Council and the National Swimming Pool Foundation (NSPF) say the problem of people urinating in pools is so bad they've launched a new campaign to educate people.

According to a new survey conducted by Survata on behalf of the Water Quality and Health Council, nearly half of Americans surveyed incorrectly believe that there is a chemical that is added to pools that turns a conspicuous color in the presence of pee.

In the same survey, 71 percent also incorrectly blame chlorine for causing swimmers' eyes to become red and irritated.

'Chlorine and other disinfectants are added to a swimming pool to destroy germs.

'Peeing in a pool depletes chlorine and actually produces an irritant that makes people's eyes turn red,' said Michele Hlavsa, chief of CDC's Healthy Swimming Program.

'The solution isn't rocket science; it's common courtesy.

'Swimmers should use the pool to swim, the restroom to pee and the showers to wash up before getting in the pool.

'It's that simple.'

'There isn't a dye that turns red.

'It's the eyes that turn red.

'Swimmers' eyes are the real color indicator that someone might have peed in a pool,' said Thomas M. Lachocki, CEO of the NSPF.

'That 'chlorine' smell at the pool isn't actually chlorine.

'What you smell are chemicals that form when chlorine mixes with pee, sweat and dirt from swimmers' bodies,' said Chris Wiant, Chair of the Water Quality and Health Council.

'These chemicals – not chlorine – can cause your eyes to become red and sting, make your nose run and make you cough.'

Half of Americans incorrectly believe chemical is polls turns urine coloured

When nitrogen-containing compounds found in pee, sweat and dirt combine with chlorine, irritants are formed.

These substances, not the chlorine itself, irritate the eyes, skin and respiratory system. In this case, more chlorine may actually need to be added to pool water to break down irritants, according to the Water Quality and Health Council.

Lachocki added that swimming keeps us happy and healthy.