Ethoxyquin
A synthetic preservative originally developed as a herbicide and rubber stabilizer, now a hidden ingredient in most fish meals.
What it actually is
A quinoline derivative developed by Monsanto in the 1950s. Prevents oxidation of fats in fish meal during ocean transport.
Why it's used in dog food
Used to keep fish meal from spontaneously combusting during shipping. Legally not required to be declared on pet food labels if added at the supplier level before the fish meal reaches the pet-food maker.
A bit of history
Approved for pet food in the 1950s. The FDA asked pet-food makers to voluntarily reduce levels in 1997 after liver-enzyme changes were reported in dogs. Banned for human food in Australia and the EU. Still legal in North American pet food.
Pros
- •Extremely effective for preserving fish meal
Cons
- •Not required to be declared on labels if pre-added to fish meal
- •Linked to liver enzyme changes and skin issues in dogs
- •Banned from human food in the EU and Australia
- •Foods using 'ethoxyquin-free fish meal' cost slightly more — a legitimate reason to prefer them
Safety notes
A food that specifically states 'ethoxyquin-free fish meal' has gone out of its way to source cleaner ingredients.
Sourcing & quality
Look for brands that explicitly commit to ethoxyquin-free fish meal (Champion Petfoods/Acana/Orijen and most Canadian raw/fresh brands do).
Commonly found in
Skip this if…
Always — choose ethoxyquin-free.
The verdict
Avoid. The fact that it can be hidden on labels makes it worth actively checking your brand's sourcing statement.