Peppermint oil is not safe for cats. It can cause severe harm if ingested, inhaled, or applied to their skin due to cats' unique metabolism which lacks certain liver enzymes needed to break down compounds in peppermint oil. Exposure can result in symptoms such as drooling, difficulty breathing, vomiting, tremors, skin irritation, lethargy, and potentially serious liver damage or respiratory distress. Even diluted peppermint oil is risky, and using it in diffusers around cats is not recommended because their strong sense of smell makes them highly sensitive to the aroma. Therefore, it is best to avoid using peppermint oil in environments with cats to prevent toxicity and health complications.