What Is TPO in Gel Polish and Why Did the EU Ban It?

September 10, 2025 Huyen Ho 1 comment

If you’ve been following nail industry news, you may have seen headlines about the EU banning TPO (Trimethylbenzoyl Diphenylphosphine Oxide) in cosmetic products. For many nail professionals, this raises important questions: What exactly is TPO? Why was it banned? And how does this affect the nail products we use every day?

Let’s break it down.

What is TPO?

TPO (Trimethylbenzoyl Diphenylphosphine Oxide) is a photoinitiator used in UV-curable products, including many gel polishes, builder gels, and nail enhancements. Photoinitiators like TPO help the gel harden (or “cure”) when exposed to UV or LED light.

In short: without TPO, many gels wouldn’t properly cure.

Why Did the EU Ban TPO?

The EU banned TPO because it has been classified as a CMR 1B substance—meaning it is suspected of being harmful to reproduction—under the EU’s classification, labeling and packaging (CLP) regulation. This classification triggered its prohibition in cosmetics, effective from 1 September 2025.

What the Scientists Found

Animal studies (particularly in rodents) given high doses of TPO via ingestion showed effects such as testicular shrinkage and reproductive toxicity. But these doses are much higher than any exposure expected from normal nail gel use. In typical gel formulations, TPO makes up only about 1-4% of the product. Also, the exposure route in animal studies (ingestion / systemic) is very different from topical exposure in nail gel application. To date, there are no published human clinical trials showing testicular or reproductive damage from standard nail gel use.

Regulatory Consequence

Because of the animal evidence plus uncertainties (especially about long-term or cumulative exposure), regulatory bodies applied the precautionary principle. They classified TPO as CMR 1B and decided that it must be banned in all cosmetic products in the EU starting 1 September 2025.

What This Means for Nail Professionals in the EU

No more TPO-based gels: Nail brands must reformulate to comply with EU laws.
Stricter imports: Salons ordering gels from outside the EU should double-check that products are TPO-free.
Potential product shortages: Some popular gels may be temporarily unavailable while companies adjust their formulas.

What About Non-EU Countries?

In places like the U.S., TPO is still allowed in nail products. However, many international brands are shifting to TPO-free formulas to meet EU standards and simplify global distribution. This means nail techs worldwide may start seeing more “TPO-free” labels.

Zurno’s KaZEN Builder Gel: 100% TPO-Free

We’re proud to share that KaZEN Builder Gel (also known as ZEN Builder Gel) is already TPO-free. That means:

You can work with confidence knowing your product is future-proof and compliant with EU standards.
No compromise on performance—KaZEN still delivers the strength, clarity, and easy application nail techs love.
It’s a safer, smarter choice for both professionals and clients.

At Zurno, safety and innovation go hand in hand. By eliminating TPO from our builder gel formula, we give salons a reliable solution that aligns with the highest standards in the industry.