Campaigners for the use of sun protection products to reduce the incidence of UV-induced skin damage (including skin cancers) are no doubt used to encountering the same objections time and again. Some desire the healthy look of a bronze tan and are prepared to run the risk of over-exposure.
There are others who complain about the inconvenience of applying sunscreen and dislike the feel of sun protection products on the skin. However, as awareness of the dangers of sun exposure is increasing, the advice from governments, and health and charity organisations, is for more regular use of products offering greater UV protection. The personal care industry needs to offer commercially viable UV protection formulations that provide the high SPFs and UVA protection levels required by an increasingly educated and regulated market. These need to be in convenient application formats with appealing sensory attributes. Today’s sun care formulator must simultaneously aim for new heights of UV performance and cosmetic elegance.
Increased demand
The increased demand for UV performance brings the need for ever higher inclusions of active sun filters. These increased levels of sun filter not only bring limitations to the formulation but also may lead to a detrimental skin feel. However, this may not be the only problem. Formulators often encounter a sun protection factor (SPF) ceiling when adding higher percentages of the UV filters to the formula results in little or no additional SPF performance. Croda’s SolPerForm 100 [INCI: Aqua (and) hydrolysed wheat protein/PVP crosspolymer] is a naturally-derived polymer based on hydrolysed wheat protein and PVP crosspolymer that improves the film-forming properties of cosmetic emulsions when spread onto skin. In the case of sunscreen emulsions, this means that the active ingredients are more evenly distributed over the skin surface, and hence are dramatically more effective. It has been proven with this new material that the high SPF levels demanded by the modern sun care market can be achieved much more easily. The uneven nature of the skin surface makes it generally difficult to achieve a truly even spread of formulation on application, and in most sunscreen products the application result is likely to be akin to that depicted in Figure 1, with some parts of the skin surface having little or no protection. It is possible to achieve moderate SPF ratings in these circumstances but attempts to significantly increase the SPF ratings of unevenly distributing formulations are likely to be doomed to failure, no matter how much additional filter is added.
Optimisation
Achieving optimum performance in a sunscreen formulation requires the active ingredients to be distributed as evenly as possible over the skin surface to approach the ideal distribution illustrated in Figure 2. Such optimisation can result in attainment of significantly higher SPF ratings without inclusion of additional UV filters, and hence without the cost burden and formulation limitations that increasing filter concentration would bring. Enhancing film formation can therefore be the key to achieving the optimum combination of superior UV performance and cosmetic elegance. The hydrolysed wheat protein/PVP crosspolymer material has been proven to dramatically increase SPF levels (in vivo and in vitro) while maintaining UVA/UVB ratios. Extensive studies have demonstrated broad efficacy across a range of formulation types including those with only inorganic sunscreens, those with only organic sunscreens and those which combine both types of filter. Croda’s formulation C10010 provides an example of how, with hydrolysed wheat protein/PVP crosspolymer one can aim for higher SPF values and hence generate better product claims, without having to radically change established formulations. This elegant spray formulation already benefits from the well-known SPF synergy between inorganic and organic sunscreens as well as a biphasal distribution of actives, which helps achieve more even skin protection by incorporating UV filters in both phases of the emulsion. In this case the formulation without the new additive gives an in vivo SPF of 41 (International method, five subjects), which, under the 2006 EU recommendations on labelling of sun care products, would be labelled as SPF 30. However, with a small addition of 2% hydrolysed wheat protein/PVP crosspolymer, the SPF is increased to 56, thereby improving the label claim to an impressive SPF 50 (see Fig. 3).
