A chemical found in some gel nail products has been prohibited in the UK and Europe because it was classified as harmful to reproduction. The ingredient, called trimethylbenzoyl diphenylphosphine oxide, or TPO, has been linked to reproductive health concerns.

This has led to questions about why products containing the ingredient are still being sold in other places.

What Is TPO and Why Is It Used in Gel Nails?

TPO, which stands for trimethylbenzoyl diphenylphosphine oxide, is a chemical used in certain UV- and LED-cured gel nail products. It acts as a photoinitiator, which means it helps the gel harden when exposed to ultraviolet or LED light during a nail treatment.

The ingredient is used because it helps gel polish cure quickly and properly under a nail lamp. Without ingredients that start this hardening process, the gel would not become solid in the same way.

However, TPO has raised safety concerns because regulators have classified it as a substance that can be harmful to reproductive health. The European Union put TPO in Category 1B for reproductive toxicity, which means available evidence supports classifying it as presumed to have reproductive toxicity.

That classification does not mean that having a gel manicure will definitely lead to infertility or other reproductive problems. It describes the hazard of the chemical itself, while the actual risk to someone depends on factors such as how much they are exposed to and how long the exposure lasts.

Why Was TPO Banned in the UK and Europe?

The European Union stopped allowing TPO in cosmetics because the chemical was classified as a Category 1B reproductive toxicant. According to EU regulations, products containing TPO have not been allowed to be sold or used professionally in the EU since 1 September 2025.

The decision was made because of concerns about how the chemical might affect fertility and unborn babies. However, the classification is based on evidence about the chemical's potential hazards and does not mean that having a gel manicure once in a while has been shown to cause infertility or pregnancy problems.

The UK also has strict rules governing cosmetic ingredients, with TPO being phased out and other substances banned or restricted. This means the rules surrounding TPO can differ between the UK, Europe and other countries.

Can TPO in Gel Nails Affect Your Health?

The main worry about TPO is how it might affect reproductive health, but it's important to consider how much of it a person is actually exposed to from a gel manicure when figuring out the risk.

People who often use gel nail products might get exposed to the gel through their skin if the gel hasn't fully cured and touches their skin. Nail technicians might be exposed more often because they use these products many times, but the actual risk can vary depending on the product, how it's used and how much they come into contact with it.

TPO isn't the only possible problem with gel manicures. Some nail products may cause skin irritation or an allergic reaction called contact dermatitis, especially if the products haven't fully cured and come into contact with the skin. Repeated exposure might increase the chances of someone becoming more sensitive over time.

This doesn't mean that people who get gel manicures should worry. By following the product instructions, keeping uncured gel away from your skin and choosing products made by trustworthy companies, you can lower the chance of unwanted exposure.

Should You Avoid TPO During Pregnancy?

Because TPO is considered harmful to reproduction, some people might be concerned about using gel nail products that contain this chemical while they are pregnant. However, the classification itself does not mean that a regular gel manicure will harm a pregnancy.

Pregnant individuals who want to be cautious might opt for nail products that don't contain TPO to minimise their exposure. It's also important to make sure uncured gel doesn't come into contact with the skin, because this can lead to more direct exposure and might cause skin sensitisation.

If you're pregnant or trying to get pregnant and worried about chemical exposure, you can talk to your nail technician about the products they use and whether they are free from TPO. If you have particular concerns about chemical exposure during pregnancy, you should also discuss them with your doctor.

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