Phenylbenzimidazole Sulfonic Acid
Phenylbenzimidazole Sulfonic Acid (also known as Ensulizole) is a chemical sunscreen agent that provides strong protection in the UVB range (280–320 nm), with peak protection at 306 nm. Unlike most sunscreen agents, it is water-soluble rather than oil-soluble, making it suitable for lightweight, non-greasy formulations. It is approved worldwide, with a maximum concentration of 4% in the US and up to 8% in the EU (Cosmetic Restriction VI/6).
Delivers strong UVB protection and is well-suited for light, oily-skin-compatible sunscreen formulas due to its water solubility. It is fairly photostable and can help protect less stable UV filters, such as the UVA blocker avobenzone, from degradation in a formula.
As a chemical UV filter, it is subject to regulatory concentration limits (up to 4% in the US, up to 8% in the EU). No additional specific cautions are noted in the source.
