Extended water exposure can cause stratum corneum swelling and a more porous skin barrier. People often apply water-resistant sunscreen formulations before extended period of water activities in the summer, to protect the skin from harmful UV rays.

A recent study published in the International Journal of Cosmetic Science aimed 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.

In this study, trans-epidermal water loss (TEWL) measurement was conducted—in a controlled water patch (including salt and chlorine water) model. This relevant model was applied to analyze the effects of pre-treatments of sunscreen sprays and stick. Additionally, water sorption-desorption test was carried out, in vivo, with and without sunscreens. The effect of constant water exposure combined with a known irritant – sodium lauryl sulphate (SLS), was studied in a randomized clinical trial.

The findings suggested that application of sunscreen formulations help mitigate water-induced barrier disruption by repelling water at skin surface. While pretreatment with sunscreen statistically decreased the irritation in an acute patch test model.

It was inferred that hydrophobic sunscreen formulations can help in protecting the skin from extended water exposure by serving as an additional water barrier.

Source: International Journal of Cosmetic Science. 2016 Apr;38(2):164-9. doi: 10.1111/ics.12271.