What Is TPO in Gel Nail Polish? Is It Safe for Human Health?

Recently, the European Union (EU) announced a ban on TPO (trimethylbenzoyl diphenylphosphine oxide) in cosmetics — including gel nail polishes — raising widespread concerns about its safety. However, experts emphasize that this ban is based on animal studies involving extremely high oral doses, and there is no scientific evidence showing that TPO harms human health when used correctly.

In this article, S&L Beauty will explain what TPO is, why it’s used in gel polish, its safety profile, expert opinions, and how to safely use gel nail products to protect your health.

What Is TPO?

TPO is short for trimethylbenzoyl diphenylphosphine oxide, a photoinitiator widely used in gel nail systems and other nail products. Its primary role is to initiate the curing process when exposed to UV or LED light, helping gel polish harden and adhere firmly to the natural nail surface.

Thanks to TPO, gel polishes achieve long-lasting durability, high shine, and superior wear resistance.

What Is the Role of TPO in Gel Nail Polish?

Within gel nail polish formulations, TPO plays a critical role in ensuring quality and performance:

• Initiates the curing reaction: Under UV/LED light, TPO produces free radicals that link monomers and oligomers together to form a solid, durable polymer network.
• Speeds up drying time: With TPO, the curing process is faster and more efficient, saving time during nail services.
• Enhances durability and shine: TPO contributes to a high-gloss finish that resists chipping, peeling, and dullness.

Without TPO or an equivalent photoinitiator, achieving the smooth, strong, and glossy finish that gel polishes are known for would be extremely difficult.

Does TPO in Gel Nail Polish Harm Human Health?

In September 2025, the EU banned TPO in cosmetics, including gel nail polishes. The decision was based on:

Animal studies showing that extremely high oral doses of TPO may lead to: Reproductive toxicity, genetic mutations, potential carcinogenic effects.

However, it’s critical to understand:

• These findings are based on oral ingestion of very high levels of TPO — not topical exposure through nail products.
• No human studies have demonstrated any health risks from TPO in gel nail polish when used as intended.

According to a comprehensive review by the Cosmetic Ingredient Review (CIR):

• TPO is typically used at concentrations up to 4% in nail products.
• After UV/LED curing, the amount of TPO that can be extracted from hardened gel is below 0.2 ppm — an extremely low, negligible level of exposure.

What Experts Say About TPO

Several cosmetic scientists and industry experts have weighed in on the safety of TPO:

Allison Leer (MD, co-founder of Botanist Nails):

“TPO is believed to be an endocrine disruptor (harmful to reproduction) however most evidence of TPO comes from animal studies so data studying the effects on humans is limited,”

Kelly Dobos (Cosmetic Chemist):

“These materials, when used as intended, are very safe because real-world exposure conditions are vastly different from experimental models.”

David Andrews (Environmental Working Group):

“The EU ban addresses hypothetical risks based on animal studies, not empirical findings from actual gel polish use.”

Doug Schoon (Nail Manufacturer Council):

“The EU’s ban is ingredient-specific, not product-wide. Gel polishes remain safe and permitted when reformulated without TPO.”

In short, TPO is not inherently dangerous, and gel polishes containing it are safe to use when handled correctly.

How to Safely Use Gel Nail Polishes Containing TPO

If you regularly use gel polishes — whether at home or in salons — following proper practices ensures safety:

• Choose trusted, certified products: Always buy gel polishes from reputable brands that comply with safety regulations.
• Apply properly: Avoid applying gel too close to the skin or cuticle. Follow curing times exactly as recommended by the manufacturer.
• Avoid direct contact with uncured gel: Exposure risk is highest before curing; once hardened, absorption is minimal.
• Use a quality UV/LED lamp: roper curing ensures that TPO fully integrates into the polymer matrix.
• Care for your nails post-manicure: Hydrate your cuticles and nails and avoid peeling or biting cured gel polish.

Conclusion

TPO is an essential photoinitiator that helps gel polishes harden, last longer, and maintain their shine. The EU’s TPO ban is based on animal studies with high oral doses, not real-world human data.

Scientific reviews show that TPO exposure from gel nails is negligible when products are used properly. At S&L Beauty, customer safety is our priority. While our formulas currently contain TPO, available research shows no evidence that TPO poses a cancer risk when used correctly.

We continuously monitor regulatory updates and are prepared to reformulate with alternative photoinitiators when needed — ensuring our products remain safe, effective, and trustworthy.

FAQs About TPO and Gel Nail Polish

1.Does TPO in gel polish cause cancer?

There is no scientific evidence linking TPO exposure from cured gel polish to cancer in humans.

2. Why did the EU ban TPO if it’s safe?

The ban is a precautionary measure based on animal studies with extremely high oral doses, not real-world usage scenarios.

3. Are gel polishes without TPO safer?

Not necessarily. Alternative photoinitiators work similarly and have similar safety profiles when used properly.

4. How can I minimize risks when using gel polish?

Use certified products, follow curing instructions carefully, and avoid skin contact with uncured gel.