Dehydration is defined as the loss of body water that exceeds the amount taken in. Chlorine, the disinfectant used to keep pool water clean, does not function as a systemic diuretic like caffeine or alcohol. The fluid loss experienced by swimmers is not a direct chemical effect on the kidneys. Instead, dehydration associated with chlorinated water is an indirect consequence stemming from the chemical’s interaction with the body and the unique environment of a swimming pool.
Chlorine’s Impact on the Skin Moisture Barrier
Chlorine is a potent oxidizing agent designed to destroy organic matter, including the protective components of human skin. When free chlorine contacts the skin, it begins to break down the natural oils, known as sebum, that coat the skin’s surface. Stripping away these oils removes a primary defense mechanism against water loss.
The chemical also disrupts the stratum corneum, the outermost layer of the skin, which is a delicate matrix of lipids and proteins. This disruption compromises the skin’s barrier function, leading to a significant increase in trans-epidermal water loss (TEWL). The body loses moisture through evaporation at an accelerated rate because the skin is no longer able to effectively retain water. This continuous, indirect fluid loss contributes to the body’s overall dehydration.
The familiar sensation of “tight” or “itchy” skin after swimming is an immediate physical manifestation of this compromised barrier. Chronic exposure can further degrade structural proteins like collagen and elastin. This makes the skin less resilient and more prone to persistent dryness and irritation, representing a primary way chlorine indirectly contributes to fluid loss.
Respiratory Effects and Internal Fluid Loss
Chlorine’s byproducts, called chloramines, are responsible for a significant amount of internal fluid loss. Chloramines are volatile compounds formed when free chlorine reacts with organic waste introduced by swimmers, such as sweat, skin cells, and urine. These chloramines off-gas from the water, creating an irritating layer of vapor, especially in poorly ventilated indoor pools.
When inhaled, these volatile compounds, particularly trichloramine, irritate the mucous membranes lining the nose, throat, and lungs. This irritation triggers an inflammatory response, leading to increased mucus production and a runny nose, which is a direct loss of body fluid. Swimmers often experience a characteristic “chlorine cough” as the body attempts to expel the irritants.
Beyond chemical irritation, the physical act of swimming contributes to fluid loss through respiration. Vigorous exercise naturally increases the rate and depth of breathing. The body must humidify the air entering the lungs, a process that expends considerable internal moisture. This respiratory water loss contributes to the fluid deficit alongside the irritation-induced mucus production.
Strategies to Maintain Hydration While Swimming
Minimizing the indirect dehydrating effects of chlorine starts with good hygiene before entering the water. Taking a pre-swim rinse helps remove sweat, cosmetics, and other organic matter that would otherwise react with the chlorine to form irritating chloramines. This simple step reduces the concentration of volatile compounds that cause respiratory irritation and subsequent fluid loss.
Active fluid intake before and during the swimming session is necessary to offset both sweat loss and the indirect chemical effects. Swimmers should aim to consume 16 to 20 ounces of water one to two hours before getting in the pool. During the swim, sipping 4 to 8 ounces of water every 15 to 20 minutes is recommended, especially for workouts lasting longer than an hour.
The post-swim routine must focus on restoring the skin’s moisture barrier that chlorine has compromised. Immediately showering with a mild cleanser is necessary to wash off residual chlorine and chloramines. Following the shower, applying a moisturizer containing barrier-repairing ingredients helps the skin regain its ability to lock in moisture, reducing accelerated trans-epidermal water loss.