Ingredient review
Phenylbenzimidazole Sulfonic Acid
INCI: PHENYLBENZIMIDAZOLE SULFONIC ACID
A widely used, water-soluble UVB filter that is generally gentle on skin but offers no UVA protection on its own.
In plain English
Phenylbenzimidazole sulfonic acid is a sunscreen ingredient that absorbs ultraviolet B (UVB) rays — the kind that cause sunburn and contribute to skin cancer. Unlike many other sunscreen filters, it dissolves in water rather than oil, so it can be used in lightweight, non-greasy formulas. It is often paired with other ingredients to provide broad-spectrum protection against both UVB and UVA rays.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is relatively strong for its common cosmetic role.
Risk flags are low for most users, though the finished product can still irritate.
- Source
- synthetic
- Evidence
- strong
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Phenylbenzimidazole Sulfonic Acid is generally a lower-concern ingredient when the full formula suits your skin.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Phenylbenzimidazole Sulfonic Acid.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
strongThere is a stronger practical or research basis for the ingredient role described here.
What it is
A synthetic, water-soluble organic compound that functions as a UVB filter in sunscreens and other cosmetic products. It is approved by the FDA as a safe and effective sunscreen active ingredient.
How it works
It absorbs UVB radiation (wavelengths 290–320 nm) and converts it into harmless heat, preventing it from penetrating the skin and causing damage. Because it is water-soluble, it is often used in gel-based or alcohol-based formulas that feel lighter on the skin.
Pros
Lightweight feel
Because it's water-soluble, it can be used in clear, non-greasy gels and lotions that won't clog pores or feel heavy.
Effective UVB protection
It reliably absorbs UVB rays, reducing the risk of sunburn and long-term skin damage.
Cons and cautions
No UVA protection
On its own, it does not shield against UVA rays, which cause premature aging and deeper skin damage. It must be paired with a UVA filter for broad-spectrum coverage.
Potential photodegradation
It can break down when exposed to sunlight, so it is often formulated with stabilizers or combined with other filters to maintain effectiveness.
Best for
- People with oily or acne-prone skin who prefer lightweight sunscreens
- Anyone looking for a water-resistant UVB filter in a daily SPF product
Use caution if
- Those seeking broad-spectrum protection without combining with a UVA filter
- Individuals with known sensitivity to organic sunscreen filters
Usage tips
Safety summary
Phenylbenzimidazole sulfonic acid is considered safe for use in sunscreens at approved concentrations. It has a low irritation and allergy risk, but like all sunscreen ingredients, it should be used as directed. It does not provide UVA protection, so it must be combined with other filters for broad-spectrum coverage.
Research notes
Numerous studies confirm its effectiveness as a UVB filter and its safety profile. Research also highlights the need for stabilization to prevent photodegradation and the importance of combining it with UVA filters for comprehensive sun protection.
Common label clues
- Typical concentration
- 1% to 4%
- Regulatory status
- Approved by the FDA as a safe and effective sunscreen active ingredient in concentrations up to 4% in the United States. Also approved in the EU and other regions.
- Common uses
- Sunscreens, Daily moisturizers with SPF, Makeup with SPF
- Environmental note
- Some studies suggest that organic UV filters may accumulate in aquatic environments, but phenylbenzimidazole sulfonic acid is generally considered less persistent than some other filters. More research is needed to fully understand its environmental impact.
Good to know
- This ingredient is often listed as 'Ensulizole' on product labels in the United States.
- It is one of the few water-soluble UV filters, making it ideal for oil-free and matte-finish sunscreens.
Common questions
What is Phenylbenzimidazole Sulfonic Acid in beauty products?
Phenylbenzimidazole sulfonic acid is a sunscreen ingredient that absorbs ultraviolet B (UVB) rays — the kind that cause sunburn and contribute to skin cancer. Unlike many other sunscreen filters, it dissolves in water rather than oil, so it can be used in lightweight, non-greasy formulas. It is often paired with other ingredients to provide broad-spectrum protection against both UVB and UVA rays.
What does Phenylbenzimidazole Sulfonic Acid do in a beauty product?
It absorbs UVB radiation (wavelengths 290–320 nm) and converts it into harmless heat, preventing it from penetrating the skin and causing damage. Because it is water-soluble, it is often used in gel-based or alcohol-based formulas that feel lighter on the skin.
Is Phenylbenzimidazole Sulfonic Acid safe for most people?
Phenylbenzimidazole sulfonic acid is considered safe for use in sunscreens at approved concentrations. It has a low irritation and allergy risk, but like all sunscreen ingredients, it should be used as directed. It does not provide UVA protection, so it must be combined with other filters for broad-spectrum coverage.
Who should be careful with Phenylbenzimidazole Sulfonic Acid?
Those seeking broad-spectrum protection without combining with a UVA filter Individuals with known sensitivity to organic sunscreen filters
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.