Red eyes, itchy skin and the chlorine smell
The strong chlorine smell at a pool is not too much chlorine. It usually means the opposite. Here is what is really irritating you, and how it gets fixed.
The assumption we're testing
“There is too much chlorine in this pool”
That smell is not chlorine
This is the one that surprises people most, and it comes straight from public health guidance rather than from us.
The sharp smell people call a chlorine smell is mostly chloramines. As the US Centers for Disease Control put it, if you smell chlorine where you swim, you are probably smelling chloramines.
Chloramines are what you get when chlorine has already reacted with something. They are a by-product, not the sanitiser.
So a strong smell does not mean the pool is over-chlorinated. It usually means there is not enough free chlorine left to finish the job.
Where chloramines come from
Chlorine reacts with whatever swimmers bring in with them. Sweat. Skin cells. Body oils. Sunscreen. Deodorant. And urine.
Two things happen at once. The chlorine gets used up dealing with all that instead of germs, and the reaction leaves chloramines behind.
It builds through a hot weekend. Friday the pool is fine. Sunday afternoon, after a dozen people have been in it, the water smells and eyes start going red.
Red eyes are usually not the chlorine either
Two things sting. One is chloramines. The other is pH.
Your eyes are comfortable in a fairly narrow range. Water that has drifted away from it will sting even when the chemistry is otherwise fine.
So red eyes after a swim point at one of two things: a pool that has been used hard and not caught up, or a pool whose pH has wandered. Neither is fixed by adding more chlorine, and one of them is made worse by it.
The same goes for itchy skin and that tight feeling afterwards. Health authorities also link chloramines to coughing and wheezing, which is why indoor pools with poor ventilation smell the way they do.
How it actually gets fixed
Chloramines do not filter out and they do not wear off on their own in any useful timeframe. They have to be destroyed.
That means oxidising them, which is what shocking a pool is for. The dose has to be high enough to break past the chloramines rather than just topping the chlorine up. A small dose does nothing except cost money.
This is the part that gets done wrong at home. People add their usual amount, the smell stays, and they conclude the pool needs less chlorine rather than one decent dose.
After that, the water needs to circulate and filter properly to clear. If the pool is also cloudy, that is a separate signal — see what your pool colour means.
What you can do about it
Most of the prevention is not chemical.
A quick rinse before swimming genuinely helps, because it takes off the sweat, sunscreen and oils that chlorine would otherwise have to deal with. Public health advice says even a minute makes a difference.
Get children to the toilet before they get in, not after they are already wet. And keep anyone who has been unwell out of the water for a while.
None of that is glamorous. It is also the cheapest pool chemistry you will ever do.
When it is not the water at all
Sometimes we test a pool that people are convinced is irritating them and the numbers are fine.
Worth ruling out: goggles that leak, an old sunscreen reacting, or simply a long swim in warm water. Chlorine at normal levels does dry skin out, and people with sensitive skin notice it more.
What we can tell you is whether the water is the cause. If it is, it gets fixed. If it is not, we will say that too rather than sell you something.
If a pool keeps doing this, it is worth a proper look at the water and the gear rather than another bucket of something.
Where this came from
Figures and rules on this page come from the sources below. Rules change, so check the current version before you act on anything here.
- US Centers for Disease Control and Prevention — Preventing eye irritation from pool chemicals
This is Water testing & balancing territory.
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