Stinging eyes at the pool: it's (almost) never too much chlorine
- Stinging eyes = pH out of range (the eye sits at 7.4) or chloramines ("spent" chlorine) — almost never an excess of chlorine.
- If there's a strong chlorine smell on top, it's chloramines for certain.
- A pH + free/total chlorine test identifies the culprit in 30 seconds.
- Correct the pH or run a shock chlorination depending on the diagnosis — doses calculated by the app.
Stinging eyes or itchy skin after a swim get chlorine blamed unfairly. In the vast majority of cases, the culprit lies elsewhere: a drifting pH — the human eye lives at pH 7.4, and any water that moves away from it becomes irritating — or chloramines, that “spent” chlorine that stings the eyes and smells strong. An excess of active chlorine is rarely to blame at family-pool levels. The reflex: test pH and chlorine (free and total), then correct what’s drifting. The exact doses depend on your pool: the CliniPool app calculates them.
The two real culprits
The pH. It’s the most frequent and simplest cause. Tears and eyes naturally sit around pH 7.4; water that’s too acidic (below 7.0) or too alkaline (above 7.6) attacks the cornea and the skin’s protective film. You can have perfectly sanitised water and red eyes, simply because the pH drifted with the rain, the swimming or the top-up water.
The chloramines. When chlorine combines with what swimmers bring in (sweat, cosmetics, urine), it forms chloramines: highly irritating to eyes and mucous membranes, and responsible for the famous “pool smell”. The tell-tale clue: if it stings AND smells strongly of chlorine, it’s them.
The diagnosis in 30 seconds
One test settles it: pH out of range → that’s your culprit, a simple correction; pH fine but total chlorine well above free chlorine → chloramines, you need a shock chlorination to destroy them; both correct → look at the water’s hardness or at individual sensitivity (contact lenses, for instance).
Correcting, according to the diagnosis
If it’s the pH: a pH+ or pH− correction brings the water back into the comfort range (7.0–7.4). The amount depends on your volume, your alkalinity and the gap to close — it’s a calculation, not a scoop: the app handles it and tells you when to re-test.
If it’s the chloramines: the remedy is a breakpoint chlorination — enough chlorine, in one go, to “burn off” the combined chlorine. Underdosed, it makes things worse; properly dosed, the smell and the irritation disappear together. The chlorine smell guide (“Also worth reading”) details the mechanism, and the app calculates the dose from your test.
Stopping it coming back
pH is monitored, not guessed: one photo test a week in season is enough to spot the drift before it stings anyone’s eyes. On the chloramine side, the shower before the swim and an oxidation after the big swimming days do most of the work. The app keeps an eye on both and warns you when the water starts to drift — before the red eyes, not after.
Frequently asked questions
Why do my eyes sting when the pool is well maintained?
The pH can drift within days (rain, swimming, top-up water) even in a well-kept pool. The human eye sits at pH 7.4: as soon as the water moves away from it, it stings — even with perfect sanitisation.
Children's red eyes after swimming — is it serious?
It's most often a passing irritation (pH or chloramines) that fades within hours. Above all, it's the signal to test and correct the water. If the irritation persists or comes with pain, seek medical advice.
Does itchy skin after a swim also come from the pH?
Often yes: a pH that's too high or too low attacks the skin's protective film. Chloramines and very hard water can contribute too.