The Effect of Antioxidants on the Photoinduced Degradation of Sunscreens

The stability of sunscreen formulations is a key factor influencing their protective efficacy and safety, particularly under UV exposure, which can induce photodegradation of UV filters. (1) Background: This study aimed to evaluate the effect of selected antioxidants (stabilized vitamin C, carrot macerate, and ferulic acid) on the sun protection factor (SPF) and photostability of sunscreen formulations. (2) Methods: Four oil-in-water creams with identical compositions, except for the antioxidant type, were prepared and characterized in terms of SPF, rheological behavior, pH, conductivity, stability, and sensory properties. SPF was determined using an in vitro spectrophotometric method before and after UV irradiation (30 and 120 min). (3) Results: Antioxidant incorporation increased initial SPF, with ferulic acid providing the most significant enhancement. After UV exposure, all formulations exhibited a decrease in SPF. However, the formulation containing ferulic acid maintained the highest absolute SPF value, indicating superior photostability. In contrast, vitamin C showed the greatest reduction in SPF, suggesting lower stability under irradiation. Physical characterization confirmed appropriate properties of the formulations, and sensory analysis identified the ferulic acid formulation as the most acceptable. (4) Conclusions: Ferulic acid demonstrated the most favorable impact on sunscreen performance, suggesting its potential as an effective multifunctional ingredient in sunscreens.