Ethoxyquin

Ethoxyquin is a quinoline-based antioxidant used as a food preservative and a pesticide (under commercial names such as "Stop-Scald"). It is commonly used as a preservative in pet foods to prevent the rancidification of fats. There has been some speculation that ethoxyquin in pet foods might be responsible for certain health problems. To date, the US FDA has only found a verifiable connection between ethoxyquin and buildup of protoporphyrin IX in the liver, as well as elevations in liver-related enzymes in some animals. It has been shown to cause mortality in fish.

It is also commonly used in spices to prevent color loss due to oxidation of the natural carotenoid pigments.