Hi Karen-
Unfortunately, the problem extends further than companies changing ingredients and not making it obvious in the new packaging. The other, bigger problem is cross contamination in the manufacturing process. A company can process their chicken based diet and then begin manufacturing their supposed “chicken free” limited ingredient diet, but since they didn’t clean the machine in between that product is now contaminated.
A study was done on this by one of the vet schools some odd years ago and all the over the counter limited ingredient diets they tested came back positive for proteins not listed on the label. The only way to be sure this is not happening, is by using an allergenic diet from the vet. The companies that make those diets sterilize the machines in between each run to prevent contamination.
