Overview: As open-water swimming, pool training, and outdoor sessions ramp up through spring, skin faces three distinct chemical stressors in a single day, sometimes in a single session. This article breaks down what chlorine, salt, and sweat each do to the skin barrier individually, what happens when they combine, and what the research says about supporting skin through a training block that includes all three.
Chlorine: a barrier disruptor with a chemistry problem
Chlorinated pool water sits at a pH of roughly 7.3 to 7.6, notably higher than skin's naturally acidic surface pH of around 5.5. That gap alone is enough to disrupt the skin's acid mantle, the thin protective film that helps regulate barrier function and resist microbial growth. Chlorine compounds also react with the lipids that make up the skin barrier, breaking down the natural oils that keep moisture locked in.
Peer-reviewed research on competitive swimmers backs this up with more than theory. A study examining the skin epithelial barrier of young elite athletes found that swimmers showed measurable differences in skin barrier markers compared to athletes training in non-water sports, and identified a specific, named condition in dermatological literature: swimmer's xerosis, barrier damage to the stratum corneum linked directly to prolonged, repeated exposure to chlorinated pool environments. The same research noted that transepidermal water loss, the standard measure of barrier integrity, can rise measurably with sustained swimming pool exposure, and that this effect compounds with training volume over time rather than resolving between sessions.
Salt: dehydration through osmosis, not damage
Seawater carries a salinity of roughly 3.5 percent sodium chloride, meaningfully higher than the salt concentration inside human skin cells. This creates an osmotic gradient: water naturally moves from an area of lower salt concentration to an area of higher salt concentration, which means prolonged skin contact with seawater actively draws moisture out of the skin rather than simply sitting on the surface. This is a different mechanism to chlorine's chemical disruption of the barrier, but the outcome, a tight, dehydrated feeling after time in the ocean, is a physiologically real result of that osmotic pull rather than a coincidence of sun and wind.
Sweat: the stressor training itself creates
Even without a pool or the ocean in the picture, training generates its own skin stressor. Sweat changes the local pH and moisture environment of the skin surface during exercise, and research measuring sweat gland activity has confirmed that skin behaves differently, physiologically, during exercise than it does at rest. Combined with friction from clothing, straps, and equipment, sweat represents a genuine third input into the same barrier system already managing chlorine or salt exposure on a swim day.
Why the combination matters more than any one factor alone
Very few people encounter just one of these stressors in isolation. A pool session followed by an open-water swim, or an ocean swim on a day that included a sweaty gym session beforehand, means skin absorbs the chemical disruption of chlorine, the osmotic pull of salt, and the pH and friction load of sweat within a short window. Each mechanism works differently, but they share a common target: the same thin barrier layer, asked to manage all three before it has fully recovered from any one of them.
What the research supports as a response
Dermatological guidance on this is consistent and grounded in the same barrier-support principles that apply to skin under any repeated stress: maintaining barrier lipid content through moisturisation, rinsing residual chlorine or salt from the skin promptly after exposure rather than letting it sit and continue drawing out moisture or reacting with skin oils, and recognising that repeated exposure across a training block has a cumulative effect rather than a fresh start each session. None of this constitutes a claim that any product treats or prevents the barrier disruption described above. It reflects an established pattern in the research: skin exposed to chlorine, salt, and sweat within the same training block is working harder than skin that encounters none of them, and responds accordingly to consistent barrier support over time.
References
- "Effects of Exercise on the Skin Epithelial Barrier of Young Elite Athletes: Swimming Comparatively to Non-Water Sports Training Session." Peer-reviewed study on swimmer's xerosis and transepidermal water loss in competitive swimmers.
- Taylor, N.A. & Machado-Moreira, C.A. "Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans."
Dermogains products are cosmetic skincare formulations only. Nothing in this article constitutes a claim that any Dermogains product treats, cures, or prevents any medical or skin condition, including swimmer's xerosis or any other condition named in the cited research. Dermogains is positioned as a post-exposure recovery product and makes no claim of protection during swimming, sun, or chlorine exposure.