Overview

• The European Union’s prohibition, effective Sept. 1, stems from a Class 1B reproductive‑toxicity classification based on high‑dose animal studies.
• TPO is a photoinitiator that drives UV/LED curing in gel polishes, typically at about 1–4% of a formula, and it is largely consumed during the curing reaction.
• Cosmetic chemists cite substitutes such as TPO‑L and 1‑hydroxycyclohexyl phenyl ketone, and manufacturers are reformulating rather than challenging the rule.
• The ingredient remains allowed in the United States, and no comparable bans are reported outside the EU.
• Dermatologists recommend TPO‑free gels or non‑UV options like nail stickers and simple protections for curing lamps, noting skin‑cancer risk from the devices appears very low.