For your skin
A water-soluble UVB filter used in lighter sunscreen emulsions. It supports the labeled SPF without adding as much oil, but it is not broad-spectrum by itself and must be paired with UVA filters.
Want the science? Keep reading ↓Mechanism of action
A water-soluble organic UV filter that absorbs primarily UVB radiation. Because it dissolves in the water phase rather than the oil phase, it can reduce the heavy or greasy feel of a chemical sunscreen, but it still requires separate UVA coverage.
Why we tier this moderate
3 cited papers across 2 countries. The mechanism is well-described and there's at least one controlled trial in the literature, but we tier this Moderate rather than Strong to stay honest about how many specific papers we cite directly.
Cited research
Barrientos N et al. Allergic contact dermatitis caused by phenylbenzimidazole sulfonic acid included in a sunscreen. Contact Dermatitis. 2019;81(2):151-152.
Bens G. Sunscreens. Advances in Experimental Medicine and Biology. 2014;810:429-463 — review of organic and inorganic sunscreen filters, their spectral roles, formulation, and safety considerations.
Leon Z et al. A reversed-phase ion-interaction chromatographic method for in-vitro estimation of the percutaneous absorption of water-soluble UV filters. Analytical and Bioanalytical Chemistry. 2008;391(3):859-866 — evaluated skin absorption of water-soluble UV filters including phenylbenzimidazole sulfonic acid.
Sources: PubMed · KCI · J-Stage · CNKI · Wanfang · SFD · MFDS · Cochrane · SCCS · CIR. Every entry points to a specific document. See methodology for what each outcome label means.