Ensulizole

Evidence by route

About this ingredient

Ensulizole (INCI Phenylbenzimidazole Sulfonic Acid, PBSA) is a water-soluble chemical UVB filter. In the EU permitted up to 8%, in the US FDA-approved for OTC sunscreens. Mechanism. Absorbs UVB radiation in the 290-320 nm range, protects skin from burns, and prevents thymine dimer formation in keratinocyte DNA. Doesn't block UVA – so it's used only in combination with UVA filters (avobenzone, ecamsule, zinc oxide) for broadband protection. Where applied. Light-texture sunscreens: fluids, sprays, body lotions, 'invisible finish' products. Especially popular in 'oily skin', 'non-greasy', 'makeup-friendly' marked formulas. In Spain – Cantabria Labs Heliocare 360, ISDIN Fotoprotector Active Unify Fluid, La Roche-Posay Anthelios. Evidence base. UVB filter efficacy confirmed by years of practice, including SPF tests per ISO 24444. At 4-8% it gives SPF 8-15 used alone; in combination with other filters – the main UVB protection contribution. Safety and controversies. CIR confirmed Phenylbenzimidazole Sulfonic Acid safe in cosmetic use. The EU permits it in leave-on products up to 8% (Regulation 1223/2009, Annex VI). Systemic absorption through intact skin is low – below the FDA threshold for additional safety studies. Photoinstability controversy. PBSA is a relatively stable UVB filter, but can weaken avobenzone stability in formulas. Modern clinical formulas solve this with octocrylene or diphenylethyl benzimidazolate for stabilization. Pregnancy and lactation – with caution. No direct evidence of harm, but during pregnancy manufacturers recommend mineral sunscreens (zinc oxide, titanium dioxide). If ensulizole is needed – safer at concentrations up to 4%. Best suited to: any skin type, especially oily and combination – thanks to the light texture. With very sensitive skin and doubts – switch to mineral filters.

Tolerability and safety

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