Ultraviolet A (UVA) radiation accounts for 95% of the total UV radiation reaching the earth’s surface and covers a wavelength range from 320 nm to 400 nm —the longest UV wavelength. UVA can penetrate though the stratum corneum to the epidermis and dermis and stimulate tanning and pigmentation, as well as cause skin aging. Although UVB is more immediately damaging to the skin than UVA, it is now recognized that sunscreen products should protect against UVA as well as UVB.
While most existing sunscreen products provide good protection against UVB, leading dermatologists have voiced concern over the lack of UVA protection offered by current sun care products. In addition, recent publications by Draelos et al. and Murphy et al. have pointed out the importance of good UVA protection in the management of photodermatoses and prevention of skin cancer.
However, optimizing the UVA performance of sunscreens is challenging, particularly for global markets since UVA performance and labeling requirements differ from one region to another, some being more difficult to meet. Consequently, sunscreen manufacturers are finding it necessary to re-formulate products to enhance UVA efficacy while maintaining a high sun protection factor (SPF).
Lab Practical: Enhanced TiO2 Dispersions
- All formulations incorporating the enhanced UVA TiO2 dispersions passed European guidelines for UVA protection.
- Enhanced UVA TiO2 dispersions showed reliable performance across a range of formulation systems.
- W/O emulsions using the enhanced UVA TiO2 tended to provide slightly higher SPF efficacy than o/w emulsions.
- SPF units increased in an approximately linear relationship to solids content; each 1% solids enhanced UVA TiO2 typically provided at least 2–3 SPF units.