A few years ago, the center began receiving reports from dog owners attributing myriad adverse effects to the presence of ethoxyquin in dog food. The reported effects include allergic reactions, skin problems, major organ failure, behavior problems, and cancer. However, there is little available scientific data to support these contentions, or to show other adverse effects in dogs at levels approved for use in dog food. As such, there is no sound scientific basis to warrant a change in the regulatory status of ethoxyquin at this time. Highest concentrations of ethoxyquin were generally found in the liver and kidneys of test animals.
Accumulation appears to occur in the fat.
Identified and unidentified metabolites of ethoxyquin were detected in the urine of test animals. Residue analysis of muscle and liver tissues and eggs of animals fed ethoxyquin-treated diets demonstrated ethoxyquin levels below tolerances. This compound is a mild skin and eye irritant in test animals. Ethoxyquin was found to significantly decrease body weight, food intake, and occasionally growth rate in rats, cows, dogs, chickens, and mice exposed to prechronic and chronic doses in animal feed. In these studies, ethoxyquin caused a significant increase in liver and kidney weights in test animals.