“Chlorine turns your eyes red in swimming pools”

Many swimmers have experienced the sting and redness in their eyes after a dip in the pool, and the common assumption points directly to chlorine as the sole cause. This widespread belief stems from the fact that chlorine is a ubiquitous chemical in pool sanitation, and its strong odor often accompanies the irritation. It's an easy connection to make, but the truth behind those bloodshot eyes is a bit more complex than just the presence of chlorine.

The actual irritants responsible for red eyes are not chlorine itself, but rather chemical compounds called chloramines. These form when chlorine, which is added to disinfect pool water, reacts with nitrogen-containing substances introduced into the pool by swimmers. These contaminants include sweat, urine, and body oils. When chlorine combines with these organic compounds, it creates chloramines, which are far more irritating to human eyes and respiratory systems than free chlorine alone.

The persistent belief that chlorine is the direct cause is also reinforced by the distinctive "pool smell" that many people associate with a heavily chlorinated pool. Ironically, that strong chemical odor is not a sign of a clean, well-sanitized pool with plenty of active chlorine. Instead, it's a tell-tale sign of a high concentration of chloramines, indicating that the chlorine is busy reacting with contaminants. A properly maintained and balanced pool, with effective filtration and good swimmer hygiene, will have minimal chloramines, resulting in little to no eye irritation and a much fainter, if any, chemical odor.