if you bought it online (ie Chewy.com) , they should give you credit if you inform them that the food did not mesh with your dog and he/she is having allergic reaction. I did that one time and they gave me credit. I asked if I should mail the leftover food and the rep told me to donate it to the shelter. Understandably, the shelter will not accept open containers for potential contamination issues. I do understand but it is a shame wasting perfectly good food and perhaps have a much higher quality than what they feed the animals (purina). They did tell me to bring it however and put it in a section where the homeless dogowners will come pick up the dog food.
This is is fantastic! Thank you so much!