Today’s sun care formulator must achieve high SPF and challenging UVA protection standards while also making products elegant to encourage consumer compliance—and cost-effective enough to be affordable in difficult economic times. Efficacy and elegance are dependent on one another; maximizing the efficacy of UV filters enables the creation of high-SPF products using minimal amounts of said filters, which allows the formulator greater freedom to optimize skin feel. Conversely, good product aesthetics encourage consumers to apply more product, therefore moving closer to the labeled SPF.
In recent years, several highly effective and broad spectrum UV filters have been developed, enhancing the formulator’s toolbox for the development of effective sunscreen formulations. However, most new UV filters are either proprietary to one user—e.g., drometrizole trisiloxane and terephthalylidene dicamphor sulfonic acid, or are still under patent and only available from one supplier, as in the case of diethylamino hydroxybenzoyl hexyl benzoate and methylene bis-benzotriazolyl tetramethylbutylphenol. These latter materials can be relatively expensive, sometimes prohibitively so for manufacturers catering to the mass market. Thus, the work described in this paper is aimed at identifying efficient UV filter combinations without incorporating proprietary or more costly materials.
There are four key requirements to designing an efficacious sunscreen formulation. These are: the right UV filters, homogenous distribution in the formulation, homogeneous distribution on the skin, and efficacy after application. These steps will be discussed here.