Opening your eyes underwater in a swimming pool is discouraged by eye care professionals due to immediate discomfort and potential health issues. Pool water is a complex, treated chemical environment, not simply purified water, and this chemical composition can immediately irritate the delicate surface of the eye. Exposure introduces chemical irritants and waterborne microbes, creating a risk that outweighs the temporary convenience. Understanding what happens when pool water contacts the eye reveals why this practice carries risk.
The Chemistry Behind Eye Irritation
The intense burning sensation and redness swimmers experience are often mistakenly attributed to an excess of chlorine, but the actual cause is more complex. Pool water is designed to maintain a specific pH level (ideally 7.2 to 7.8), similar to the natural pH of the human eye (around 7.4). If the pool’s pH falls outside this narrow comfort zone, the imbalance alone causes immediate stinging and irritation.
A more significant irritant is chloramines, compounds far more irritating than chlorine itself. Chloramines form when chlorine reacts with organic matter introduced by swimmers, such as sweat, urine, and skin cells. These compounds are the source of the distinctive “pool smell” and cause the painful chemical reaction in the eyes.
The eye’s natural defense is the tear film, a thin protective layer covering the cornea. Exposure to chloramines strips away the tear film’s components, leaving the cornea exposed and dehydrated. This leads to redness, a gritty sensation, and temporary blurry vision, known as “swimmer’s eye.” Repeated exposure can lead to chronic dry eye symptoms or persistent inflammation.
Pathogens and Infection Risk
Beyond chemical irritation, opening your eyes in the pool introduces a risk of infection from waterborne microbes. Even in well-maintained pools, chlorine does not instantaneously kill every pathogen, especially if disinfectant levels are depleted by organic contaminants. This allows bacteria, viruses, and parasites to survive and cause illness.
A common consequence is infectious conjunctivitis, or pink eye, caused by bacteria or viruses in the water. This highly contagious infection causes redness, itching, and discharge. A much more serious, though rare, threat is Acanthamoeba keratitis, a painful, vision-threatening corneal infection caused by a microscopic amoeba found in water.
This infection is a particular risk for individuals wearing contact lenses. Lenses can trap contaminated water and the amoeba against the cornea, significantly increasing the likelihood and severity of the resulting damage.
Prevention and Post-Swim Care
The most effective protection is using properly fitting swim goggles or a swim mask, which create a watertight barrier against pool water and its irritants. Goggles prevent the chemical destruction of the tear film and block the entry of harmful pathogens. If you require corrective vision, prescription goggles ensure clear sight without the need for contact lenses, which should be removed before entering the water.
After swimming, immediate post-swim care is necessary to wash away residual chemicals and microbes. Rinse your eyes with clean, fresh water or, preferably, a sterile saline solution or lubricating eye drops. These options restore the eye’s natural moisture and pH balance more effectively than tap water. Using preservative-free lubricating drops both before and after swimming can help reinforce the protective tear film.
You should seek medical attention if irritation persists for more than a few hours or if you experience specific symptoms. These signs include persistent eye pain, blurred vision that does not quickly resolve, or any thick, watery, or pus-like discharge. Early intervention is important if chemical irritation has progressed into a bacterial or viral infection.