Facial swelling and hives?

My 11 month old puppies, I changed their food from chicken to lamb on Friday. I think that one of my puppies is allergic to it. I came home last night at 10 picked my husband up and we put the puppies in their crate. She looks fine, came home at 330 and her face was swollen a lot like a bubble. She ran around and played for a little. Gave her some Benadryl and when we woke up at 9 her swelling went down. Now her face is a tiny bit swollen but she has what looks to be little red hives all over. They are itching her bit I put ice on it to help. After the Benadryl it's edema to lessen up. How long until the hives go away and what do you think it could be? Could it just be the food allergy or no? Thank you!