Formulating broad-spectrum sun care products

Most recently, increasing documentation of UVA light spectrum effects have prompted a shift toward broad-spectrum sun care products designed for protection in both the UVB and UVA ranges of the light spectrum. One of the primary challenges formulators face in creating such products, however, is the limited number of commercially available UVA sunscreens proven to be effective and efficient in the UVA range. Further compounding the formulation of new broadspectrum sun care products is the relative lack of synergy between UVB and UVA sunscreens. Synergy among sunscreen technologies helps to simplify the formulation of photostable, long-lasting broad-spectrum sun care products. This article looks at strategies for optimising broad-spectrum formulations with hydroxyphenyl triazine chemistry, a highly compatible sunscreen technology offering protection in both the UVA and UVB ranges.

Hydroxyphenyl triazine chemistry

Most sunscreen technologies have the capability of absorbing UVB or UVA efficiently, but not both. Hydroxyphenyl triazine chemistry is distinct in that it absorbs ultraviolet radiation across a broad spectrum – both short-wave UVB radiation (290-320 nm) and long-wave UVA radiation (320-400 nm). This broad spectrum absorption is made possible by the asymmetrical molecular structure of hydroxyphenyl triazine. The asymmetrical molecular design enables two absorption peaks, one in the UVB spectrum and another in the UVA spectrum. Figure 1 shows the asymmetry of the hydroxyphenyl triazine molecule and Figure 2 shows the two distinct absorption peaks of hydroxyphenyl triazine across the UV spectrum.