Last Updated on September 29, 2026 by Giorgia Guazzarotti
Chances are you’ve never heard of Ensulizole. Also known as Phenylbenzimidazole Sulfonic Acid, Ensulizole is a water-soluble chemical sunscreen filter that mainly protects skin from UVB rays. If you’re here, you’ve probably spotted in on a sunscreen label and are wondering what it does and if it’s safe. As it often happens, the safest, hardest-working ingredients are often the ones that don’t get any press. Time to fix that, don’t you think? Here’s all you need to know about Ensulizole in sunscreen:
What Is Ensulizole?
Ensulizole is the nickname for Phenylbenzimidazole Sulfonic Acid, a chemical UV filter. In the form of free acid, ensulizole (phenylbenzimidazole sulfonic acid) is poorly soluble in water. That means it’s a pain to formulate with so cosmetic chemists don’t like to use it. And who can blame them when there are better alternatives?
In your sunscreen formulations, you’re more likely to find one of its salts forms. Soluble in water, this form of Ensulizole retains all its photo protective properties but feels lighter and non-greasy even on oily skin. Win win.
Ensulizole Benefits: What Does It In Sunscreens?
I’ve kinda given this away already. You know Ensulizole is an UV filter. But how well does it protect you from the sun? Ensulizole is mainly a UVB filter. It does a great job at absorbing and transforming them into a less damage form of energy (heat) before they can wreak havoc on your skin.
With UVA rays, things get a little trickier. Ensulizole protects skin from short UVA (UVA-2) but not long UVA (UVA-1) rays. That’s a problem because UVA-1 makes up most of the UVA radiation that reaches your skin and penetrates deeper into it, where it contributes to premature ageing, pigmentation and skin cancer.
You know what that means? You can’t use Ensulizole alone. You need to add at least one other UVA filter, like Avobenzone or Zinc Oxide, to the sunscreen to give it broad spectrum protection.
Related: Is Zinc Oxide The Best UV filter ever?
SHOP SUNSCREENS
Is Ensulizole Good For Oily Skin?
Yes. If you have oily skin and hate the thick, greasy feel of traditional sunscreens, Ensulizole has one big thing going for it: it’s water-soluble. Research shows it works well in water-based systems, while many other chemical UV filters dissolve in oils.
The result? They can make lighter, less greasy sunscreens that protect your skin without making it look like you’ve dipped your face into a frying pan. Win win. Of course, Ensulizole is only one ingredient. If the rest of the sunscreen is packed with rich oils and emollients, it can still feel greasy as hell. Always judge the whole formula, not one UV filter.
Related: The Best Skincare Routine For Oily Skin
Is Ensulizole Stable?
The problem with most chemical UV filters? They’re super unstable and degrade quickly when exposed to sunlight. Take Avobenzone, for instance. After a couple of hours under the sun, it becomes totally useless. That’s why you need to reapply sunscreen every 2 hours…
Ensulizole fares better than most UV filters here. The little research on it shows it doesn’t degrade much. Best of all, it may even help other UV filters (hello Avobenzone!) from degrading so fast, too!
Related: Is Avobenzone In Sunscreen Dangerous?
Does Ensulizole Have Any Side Effects?
Good news: Ensulizole has a good safety profile. A 2025 Australian safety review classified Phenylbenzimidazole Sulfonic Acid as low risk at the levels used in sunscreen. Sure, like any other ingredient out there, it can cause irritation or an allergic reaction in some people. But these cases are rare. This is an UV filter you can use safely – even if you have sensitive skin.
Related: Why Mineral Sunscreen Is Better For Sensitive Skin
What Are The Best Sunscreens With Ensulizole?
- Cosrx Aloe Soothing Sun Cream SPF50 PA+++ ($13.72): A hydrating sunscreen with soothing ingredients to protect from UV rays, reactive oxygen species and irritations. Available at Look Fantastic, Sephora, and Yes Style
- Eucerin Photoaging Control Sun Fluid SPF 50 (£24.95): A simple, hydrating sunscreen that protects from both UVA and UVB rays. Available at Escentual, Look Fantastic, Sephora and Walmart
- Missha All-Around Safe Block Essence Sun SPF 45 PA+++ ($13.94): A lightweight, broad-spectrum sunscreen loaded with antioxidants and soothing ingredients. Available at Walmart and Yes Style
The Bottom Line
Ensulizole is a common, stable UV filter with a good safety profile. In other words, proof that not all chemical UV filters are bad for you. But you can’t use it alone. Make sure your sunscreen has at least another UVA filter.