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Ensulizole

Also known as: Phenylbenzimidazole Sulfonic Acid, PBSA

A primarily UVB-filtering sunscreen ingredient; monograph marketing conditions and requests for more safety data are different regulatory questions.

Screenprint illustration of a plain tube and watery gel swatch
Editorial illustration

Ensulizole, also named phenylbenzimidazole sulfonic acid, is a sunscreen filter mainly associated with UVB protection. The U.S. monograph lists up to 4%, while FDA's broader proposed safety reassessment calls for additional data. Needing more data is not the same as the final 2026 removal of PABA, and a single filter does not establish a product's broad-spectrum protection.1, 2, 3

  • Also called phenylbenzimidazole sulfonic acid.1
  • The U.S. sunscreen monograph lists ensulizole up to 4%.2
  • FDA's broader proposed reassessment requests additional safety data for this filter.3

What is Ensulizole?

A permitted marketing condition and a proposed reassessment should not be collapsed into either an absolute safety guarantee or an ingredient-ban claim. Ensulizole is useful as a case study in that distinction. Its relatively water-soluble chemistry also does not make the finished sunscreen automatically water-resistant.1

Where it comes from

Natural sources

  • Not a botanical sunscreen or dietary nutrient.

How it's made

Manufactured organic UV filter formulated and neutralized as required by the sunscreen system.

What it does in products

  • UVB filtering within a sunscreen formula

Benefits

UVB contribution in tested sunscreens

moderate evidence

Ensulizole can contribute UVB filtering, but a product's actual SPF and broad-spectrum claims depend on finished-formula testing.1, 2

PubChem supports chemical identity and filtering properties, not clinical cancer prevention. The FDA monograph defines product conditions and tests; it does not assign broad-spectrum protection to ensulizole alone.

Evidence scope and limitations

Ensulizole identity, U.S. M020 conditions and FDA's current explanation checked October 1, 2026; no raw-filter or product-specific SPF claim.

  • PubChem is used for identity and basic filtering properties, not clinical efficacy.
  • Regulatory reassessment is ongoing and may change.
  • A filter list cannot establish a particular product's protection.

Evidence last checked: 2026-10-01

Side effects & safety

Sunscreen irritation or an individual reaction (varies)This guide does not assign a population allergy rate or guarantee tolerance of every formula.

Safety considerations

  • Other filters and the vehicle contribute to protection; changing or diluting the formula can invalidate tested performance.
  • Not for: Follow product warnings and avoid raw UV-filter use.
  • Not for: Do not read the request for more safety evidence as proof that sunscreen should be abandoned.
3, 2

Amounts studied & product use

These figures describe research or common product use, not a personal dose or treatment recommendation.

In skincare studies and products

M020 lists ensulizole up to 4% under its conditions. This is not a standalone SPF equation, a recommended DIY concentration or evidence that a lower-percentage product necessarily offers less protection.

2

Regulatory status

  • M020 lists ensulizole under monograph conditions. FDA's current explanation retains the distinction between a broader proposed additional-data reassessment and the finalized September 2026 removal of PABA/trolamine salicylate.
  • INCI name on cosmetic labels: Phenylbenzimidazole Sulfonic Acid.
2, 3

Water-soluble does not mean water-resistant

Solubility describes the ingredient; water resistance is a tested claim about the finished sunscreen. The two terms answer different questions.

Likewise, the filter's main wavelength coverage does not substitute for a broad-spectrum statement on a tested product. Protection depends on the system of filters, application and the label's directions.

1, 2

Frequently asked questions

Is ensulizole alone broad spectrum?

Its main filtering role is UVB-oriented. Broad-spectrum performance belongs to the finished sunscreen and its required testing, not one ingredient name.1, 2

Did the 2026 PABA decision also remove ensulizole?

The cited final action removed PABA and trolamine salicylate. FDA discusses ensulizole separately in the broader proposed additional-data reassessment.3

The bottom line

Use the complete sunscreen's tested claims. Keep current marketing conditions, proposed reassessment and finalized removals distinct.

References

  1. Ensulizole: compound summary. PubChem, National Library of Medicine (2026) · ingredient monograph · CID 33919; identity and UV-filter properties only
  2. OTC Monograph M020: Sunscreen Drug Products for OTC Human Use. U.S. Food and Drug Administration (2026) · government guidance · M020; interpret with subsequent final orders
  3. Questions and Answers: FDA's regulatory actions on over-the-counter sunscreen. U.S. Food and Drug Administration (2026) · government guidance · Final Order OTC000008-1; September 10, 2026

Revision history

  1. Initial AI-assisted evidence compilation with source-linked claims, formulation distinctions and explicit research limitations; not independent medical review.