Personally, if I had been told that my dog had allergies and a RX food was prescribed by my vet and the symptoms did not improve within a short time I would have looked for a change. Pebbles has food allergies and I was very lucky to change to Natural Balance with very good results and saw a huge improvement within a few days. Originally she was eating NB Sweet Potato and Venison but they changed the formula without me noticing. It was only a few days and she was scratching and biting her paws which lead me to discover they changed how they added the sweet potato. After trying a few different varieties within the NB line of foods and her allergies continuing I finally settles on Brown Rice and Lamb and we have had no allergy issues since.
I recommend the NB for allergies because of the success that I have had with Pebbles. While changing food I did discuss with my vet his opinion on the food and came to find he also feed NB to his rescue Greyhounds.
NB can be purchased at Petco and they even have a refund policy if the food does not agree with your pet for any reason. I've taken them up on this in the past while trying to find the proper food to help Pebbles.
As suggested previously, I too believe your vet should be involved with a RX food change.
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