Impact of the Composition of Cosmetic Formulations on the Skin Barrier and Film-Forming Potential of a Skin-Protective Biopolymer.

Air pollution-associated skin damage has increased interest in cosmetic strategies that support skin barrier function. However, the performance of film-forming properties biopolymers can be influenced by cosmetic formulation composition. In this context, this study aimed to develop and characterize gel and gel-cream formulations with or without 1% of tara and red algae-derived biopolymer. These formulations were evaluated for rheological, texture profile, sensory properties, and short-term clinical efficacy. All formulations remained stable for 28 days, with pH values between 5.0 and 5.5. The addition of biopolymer in the formulations was associated with lower consistency index values, from 79.6 ± 1.4 to 46.9 ± 0.7 in gels and from 192.1 ± 1.1 to 156.1 ± 0.9 in gel-creams. Firmness, consistency, and viscosity index were also lower in the formations added with biopolymer. The work of shear parameter was not significantly changed and biopolymer did not alter the sensory properties of the formulations. In the short term clinical efficacy study, significant increases in stratum corneum water content and reductions in transepidermal water loss were observed at 1 h for the gel containing the biopolymer and at 2 h for the gel-cream containing the biopolymer (p < 0.05). At 2 h, both formulations significantly improved smoothness, roughness, and scaliness parameters of skin microrelief compared to baseline values, and the gel-cream containing the biopolymer significantly improved smoothness when compared to its vehicle (p < 0.05). Overall, the gel showed an earlier skin barrier-related response, whereas the gel-cream showed the clearest vehicle-controlled effect on skin smoothness. Film formation was inferred indirectly from rheological and skin biophysical findings. Direct film characterization and longer-term studies are required to confirm the proposed mechanism and persistence of the effects.