08/09/2025
The TPO drama explained…
What is TPO?
TPO, or trimethylbenzoyl diphenylphosphine oxide, is a hardener found in most gel nail polishes. TPO is used to harden gel-based ingredients. It’s found nail polish that needs to be cured using UV light or LED. It’s also used in dentistry. It absorbs the light and it sends off a kind of chemical reaction that causes that gel solution to harden.
What’s the TPO drama?
As of September 1,the European Union prohibited the use or sale of gel polishes containing TPO in professional settings such as nail salons.
Why?
Due to a study conducted over six months in 2018 where male and female rats were FED (read again, FED) varying doses of TPO. The rats that ate TPO developed liver dysfunction, shrunken te**es, and fluid buildup in the lungs. Additionally, all of the female rats that were fed high doses of TPO did not get pregnant during a controlled mating period.
As a result, there are claims that TPO can cause reproductive toxicity based on animal studies. The European Union is known for its better-safe-than-sorry approach to cosmetics regulation. Once there is enough data suggest—not prove—that an ingredient is harmful to humans (like an animal study), it’s banned.
The US tends to gather more robust data before deciding to pull something off of the market. Thus a ban in the US is unlikely soon as there is no human data yet.
Please keep in mind that in the study TPO was FED to the rats, not applied to the rats topically (as it would be for a manicure) or repeatedly inhaled over time (similar to the exposure a nail technician would have).
So while the EU ban was done in the interest of our safety, more research is needed before we know if TPO is actually harmful to humans.
Are there TPO-free nail polish alternatives?
Yes. TPO-free gel polish may over time become the norm rather than the exception.
In summary…
Whether or not TPO-containing gel polish is harmful to humans remains unknown. If you’re worried, you can switch to TPO-free polishes.