Did they tell you what ingredient the dog may be reacting to? To avoid future reactions, it is important to find this out.

My friend has a Great Dane with several different allergies, including grass and chicken. Her reactions tend to be more skin related, not digestive. However, to solve the food allergy issue they switched her to Nutro Lamb and Rice (same as mentioned in above post). It is one of the few products out there, that does not include chicken meal of any kind. She is doing great on her new food. It may be worth a try for you, as well, but be sure to be careful when switching foods. Gradually mix in new food, to give pupper tummies time to adjust.

I hope the doggy feels better soon.