Assessment of homogeneity and UV filter skin retention

Sunscreens have been used for more than a century to protect the skin against the harmful effects of ultraviolet radiation. Although the beneficial role of sunscreens in protecting the skin, there is increasing evidence of UV filters’ systemic absorption and environmental repercussions. Sunscreen formulators are now facing the challenge of increasing sunscreen performance while decreasing the UV filter concentration.

In a collaborative study with a customer we evaluated the ability of a raw material in increasing the homogeneity of application and the retention on skin of UV filters. In order to reach this goal, a preliminary study on 6 subjects was carried out using two simple and reliable techniques: UV fluorescence emission and the skin stripping technique. 

The test product demonstrated a better homogeneity of application (≈50%) and a better retention on skin than the base formula containing only the UV filters. These results were confirmed by the SPF measurement (5.2 points higher than the base cream plus UV filters).