Sunscreen formulations may serve as additional water barrier on skin surface: a clinical assessment

Extended water exposure can cause stratum corneum swelling and a more porous skin barrier. People often wear water-resistant sunscreen formulations during extended period of water activities in the summer to protect skin from harmful UV rays. We wanted to evaluate whether sunscreen formulations can also serve as additional water barriers to help mitigate the disruption in stratum corneum caused by constant exposure to water.

We conducted trans-epidermal water loss (TEWL) measurement in a controlled water patch (including salt and chlorine water) model and then applied this relevant model to study the effects of pre-treatments of sunscreen sprays and stick. We also conducted water sorption-desorption test in vivo with and without sunscreens. Finally, we studied the effect of constant water exposure combined with a known irritant, sodium lauryl sulphate (SLS), in a randomized clinical trial.

We found that application of sunscreen formulations help mitigate water-induced barrier disruption by repelling water at skin surface. Pre-treatment of sunscreen also statistically decreased the irritation in an acute patch test model.

Hydrophobic sunscreen formulations can help protect skin from extended water exposure by serving as additional water barriers.