Ethoxyquin

This is the most debated preservative in pet food. The verified facts: it builds up a pigment (protoporphyrin) and raises liver enzymes in some animals — dogs are more sensitive than rats — though no clear illness has been pinned to those changes. The US FDA still permits it but asked makers to halve the dog-food limit to 75 ppm back in 1997; the EU suspended it entirely in 2017 over data gaps and an impurity, not proof of harm. The catch: it’s often added to fish meal before it reaches the factory, so a fish-based food can contain it without “ethoxyquin” on the label. If it’s listed, it must say “ethoxyquin, a preservative.” Plenty of brands have dropped it; the facts are mixed and the choice is yours.