The sting comes from chlorine’s chemical leftovers
The sharp, burning pool-water reaction is often blamed on chlorine itself. But a common culprit is chloramine: a family of compounds formed when chlorine-based disinfectants react with nitrogen-containing material swimmers bring into the water. Sweat, skin cells, and urine can all contribute. The chemistry is unpleasant, but it does not mean that urine alone caused your red eyes.
How the irritation reaches your eyes
Chlorine is added to pool water to kill germs. As it reacts with contaminants, it can form different chloramines. Some can escape from the water into the air, especially just above a busy pool. These airborne irritants can bother the delicate surface of the eye, disrupting its tear film and inflaming the conjunctiva—the thin membrane covering the white of the eye and lining the eyelids. The result can be stinging, watering, and redness.
Pool water’s pH and disinfectant levels also affect eye comfort, so redness is not a chemical test for chloramines. Still, a strong “chlorine” smell can be a clue that disinfectant has reacted with contaminants: that familiar odor often comes from chloramines, not simply from clean chlorine in the water.
Why the air matters
Because some chloramines leave the water and collect in the air, ventilation matters as much as water treatment. A crowded indoor pool can let irritants build up above the surface, where swimmers breathe and open their eyes. The memorable takeaway is that the sting may be caused by what the disinfectant has reacted with—not by chlorine doing its job alone.
