Phenylbenzimidazole Sulfonic Acid

Also known as: Ensulizole (PBSA)

INCI: Phenylbenzimidazole Sulfonic Acid | Function: Chemical UV Filter (UVB) | Type: Chemical sunscreen (benzimidazole)

What Is Phenylbenzimidazole Sulfonic Acid?

Phenylbenzimidazole Sulfonic Acid (Ensulizole) is a water-soluble chemical UVB filter that provides primarily UVB protection (280-320nm). It is often used in combination with other UV filters for broad-spectrum coverage. Water-soluble, making it suitable for light, non-greasy sunscreen formulations.

Key Skin Benefits

+ Effective UVB protection (280-320nm)
+ Water-soluble — enables light, non-greasy textures
+ Works well in combination with other UV filters
+ Photostable in formulation (with stabilizers)
+ Approved worldwide for sunscreen use

Pros

+ Water-soluble — unique among chemical UV filters
+ Enables transparent, non-whitening sunscreens
+ Suitable for oily and acne-prone skin
+ Good safety profile at approved concentrations
+ Approved up to 8% in EU and 4% in US

Cons

− Primarily UVB protection (needs UVA filters)
− Requires neutralization (triethanolamine) for solubility
− Can sting eyes in some formulations
− Moderate photostability (may need stabilizers)
− Free acid form requires pH adjustment

Specifications

Property	Value
Usage Areas	Face, Eye, Body
Product Type	Leave-On
Source	Synthetic
Natural Level	Synthetic

Safety Ratings

Metric	Rating
Skin Sensitivity	1/5 (low)
Comedogenic Rating	0/5
EWG Score	3/10

Regional Regulatory Limits

Region	Leave-on %	Rinse-off %	Status
EU (CosIng)	Max 8% (as acid)	Max 8%	Allowed — Annex VI
US (CIR/FDA)	Up to 4%	Up to 4%	Allowed — FDA OTC monograph
Japan (MHLW)	Max 3%	Max 3%	Allowed
ASEAN	Max 8%	Max 8%	Allowed — follows EU
China (NMPA)	Max 8%	Max 8%	Allowed

Typical Usage % by Product Type

Product Type	Typical %
Sunscreen (SPF)	1 - 4% (US) / 1 - 8% (EU)
Day cream with SPF	1 - 3%
Combination sunscreen	2 - 4%

References

Nash JF (2006) — Sunscreen safety evaluation. PMID: 16465376
Kockler J et al. (2012) — UV filters review. PMID: 22931553
EWG Skin Deep — Score 3/10

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