Red Eyes and a “Too Much Chlorine” Smell: The Real Culprit Is Chloramines

You get out of the pool with red eyes, and the water has a strong chlorine smell? Most people assume there is “too much chlorine.” In reality, it is almost always the opposite: these symptoms indicate a lack of effective chlorine and a buildup of chloramines. Here is why it happens, and how to fix it.

The myth: “If it smells like chlorine, there must be too much”

Properly disinfected water has almost no smell. The sharp, typical “pool chlorine” smell does not come from free chlorine, which is the chlorine that actually works. It comes from chloramines, also called combined chlorine. They form when chlorine reacts with sweat, urine, sunscreen, saliva, and other contaminants introduced by swimmers. The more chloramines there are, the stronger the smell becomes, and the more they irritate the eyes, skin, and respiratory system.

In other words: a strong “chlorine” smell is a sign that your chlorine is already exhausted from fighting contaminants, not that there is too much of it.

Why your eyes are really burning

Two main causes combine:

1. Chloramines. They, not free chlorine, are what irritate the eyes and mucous membranes.

2. Unbalanced pH. The human eye is comfortable at around a pH of 7.4 — exactly the target for a well-balanced pool. When the pH drifts, especially when it gets too low, the water becomes irritating even without chloramines. Water that “stings” is often simply water with the wrong pH.

The solution: superchlorination, also known as shock treatment

To destroy chloramines, you need to perform a shock treatment, also called superchlorination or breakpoint chlorination. The idea is to add enough chlorine to pass the threshold where chloramines are oxidized and eliminated. A regular shock treatment, for example once a week or after heavy pool use, keeps combined chlorine under control.

Basic steps:

- Test your water to measure free chlorine, total chlorine, and pH. The difference between total chlorine and free chlorine gives you combined chlorine, which represents chloramines. Above 0.3 to 0.5 ppm of combined chlorine, shock treatment is needed.

- Adjust the pH first to around 7.2–7.4 so the shock treatment can work effectively.

- Superchlorinate with an appropriate shock product, either chlorine-based or a non-chlorine shock such as monopersulfate for a gentler oxidation.

- Run the pump for several hours and wait until the chlorine level returns to a safe range before swimming.

How to prevent red eyes from coming back

- Maintain a stable free chlorine level within the proper range instead of allowing the water to “run out” of chlorine between treatments.

- Keep the pH around 7.4 — this combines eye comfort with chlorine efficiency.

- Encourage a quick shower before swimming: less sweat, sunscreen, and residue means fewer chloramines.

- Perform regular maintenance shock treatments, especially during hot weather and after busy pool days.

Test regularly, ideally with a tool that does the calculations for you. Our analysis tool turns your readings into precise treatment doses.

Try it here:

In summary

Red eyes and a strong chlorine smell do not mean “too much chlorine.” They point to chloramines and poorly adjusted pH. The answer is not to reduce chlorine, but to shock the water and balance the pH. Properly maintained water is clear, gentle on the eyes, and almost odorless.

Not sure about your diagnosis? Bring a water sample to Barracuda in Gatineau: we will tell you exactly what to do for comfortable water all summer long.