You can open your eyes in a saltwater pool, but comfort depends on the pool’s chemical balance and salt concentration. A residential saltwater pool is fundamentally different from the ocean, as its salinity is only a fraction of seawater. While the experience is gentler than a traditional chlorine pool, irritation can still occur due to chemical and biological factors affecting the eye’s surface.
Why Water Irritates the Human Eye
The surface of the human eye is protected by a tear film, a thin layer of fluid that is naturally slightly salty, or isotonic. This specific concentration of dissolved particles is matched to the cells of the eye to maintain their structure and function. When the eye contacts external water, the process of osmosis is triggered. Osmosis is the movement of water across a semipermeable membrane toward the side with the higher concentration of solutes.
Irritation and redness result directly from this disruption to the isotonic balance. If the water is pure (hypotonic), eye cells absorb excess water, causing them to swell, which leads to temporary blurring and discomfort. If the water is too salty (hypertonic), such as in the ocean, eye cells lose water to the surrounding fluid, causing them to shrink and leading to a stinging sensation. In both cases, the protective tear film is washed away, leaving the corneal surface exposed to irritation.
Comparing Pool Salinity to Natural Tears
The reduced irritation from a saltwater pool is due to its salinity being closer to the salt content of natural tears. Human tears have a salinity of approximately 0.9% sodium chloride, which is the isotonic solution for the eye. In contrast, the ocean is significantly saltier, with an average salinity of about 3.5%.
Residential saltwater pools operate at a lower salinity level, ranging from 2,700 to 3,400 parts per million (ppm), with 3,200 ppm being optimal. This range translates to a salt concentration of about 0.27% to 0.34%. Because this level is less than half the salinity of the human tear film, the osmotic difference is minimized compared to highly chlorinated freshwater or the ocean. This reduced concentration difference means eye cells do not experience the same degree of osmotic shock, resulting in a milder sensation.
Hidden Irritants in Saltwater Systems
Despite the name, saltwater pools are not chlorine-free; they generate chlorine through electrolysis. A salt chlorine generator uses electricity to convert the salt in the water into chlorine, which acts as the sanitizer. The source of eye irritation in both traditional and saltwater pools is often not the salt or the chlorine itself, but the chemical byproducts.
When chlorine reacts with organic contaminants like sweat, cosmetics, or urine, it forms compounds known as chloramines. Chloramines are volatile chemical irritants responsible for the unpleasant chemical smell often associated with a “clean” pool, and they are the primary cause of eye redness and stinging. An improper pH balance in the pool water can also cause discomfort, as a low pH means the water is more acidic and can mimic the stinging sensation of an imbalanced chemical level.
After-Exposure Care and Eye Health
If you experience mild irritation after opening your eyes in the pool, simple care can quickly restore comfort. The first step is to flush the eyes thoroughly with clean tap water to rinse away residual pool water or chemical irritants. Following the rinse, applying over-the-counter lubricating eye drops, referred to as artificial tears, can help re-establish the eye’s natural tear film.
These drops restore the balance of the tear layer, which protects the corneal surface from drying out. Most minor redness and dryness are temporary and resolve within a few hours. If you experience persistent symptoms, such as significant pain, discharge, extreme light sensitivity, or lasting blurry vision, consult a healthcare professional. These can be signs of a more serious irritation or infection.