How much lemon would be toxic enough to potentially kill a cat?

Lemons are toxic to cats, and even a small amount can be harmful. The toxic component in lemons is psoralen, which can cause symptoms like vomiting, diarrhea, and dehydration in cats. In severe cases, ingesting a large amount of lemon could potentially be fatal to a cat. It is important to keep lemons and other citrus fruits away from cats to prevent accidental ingestion.