Corn, wheat and soy are the top three ingredients that cause allergies in dogs.
I would steer clear of Science Diet. If you look in the ingredients in Z/D, you will see it contains BHA and Ethoxyquin which are toxic chemicals:
Ethoxyquin
Promoted kidney carcinogenesis.
Significantly increased incidence of stomach tumors.
Enhanced bladder carcinogenesis.
BHA
Enhanced stomach and urinary bladder carcinogenesis.
Causes squamous-cell carcinomas in stomachs.
(Cancers of this type are among the most lethal and fastest acting, the swiftest effects being seen among animals with light colored fur.)
BHT
Promoted urinary bladder carcinogenesis.
Could be a promoter of thyroid carcinogenesis.
Studies have noted that BHA and other antioxidants, particularly Propyl Gallate and ethoxyquin, showed additional effects in inducing stomach hyperplasia and cytotoxicity.
According to Dr. Wendell Belfield, DVM, practicing veterinarian for some 26 years, both BHA and BHT are known to cause liver and kidney dysfunction and are banned in some European countries. He adds that ethoxyquin is suspected of causing cancer and that propylene glycol (a pet food ingredient closely related to anti-freeze) causes destruction of red blood cells.
Ethoxyquin is listed and identified as a hazardous chemical by OSHA. It has a rating of 3 on a scale of 1 to 6, with 6 being super toxic requiring less than 7 drops to cause death. When manufactured by Monsanto, the containers are marked with the word POISON. Monsanto makes no representations and will not be responsible for damages of any nature whatsoever. The Department of Agriculture lists and controls Ethoxyquin as a pesticide.
http://www.canine-epilepsy-guardian-...ogy_of_bha.htm http://www.hillspet.com/zSkin_2/prod...=1201036880378