Sounds like a bee/wasp sting in or near the mouth.
Once the reaction starts, the body's immune system actually escalates the situation. AJ's human has good info in her post. Anaphylaxis, or symptoms very similar can occur from a sting on the face, throat, or in the mouth, when normally the dog doesn't react so sever when stung on other parts of the body.
Hope Gizmo is feeling better. If hives continue to come and go in greater and lesser severity, but not go away, you may consider a round of prednisone and benedryl for about a 10 day period. Most Vets will do this with a phone call request so it saves you the office visit charge. If this is the routine your vet puts Gizmo on, be prepared for a much larger intake of water, and frequent pees (or perhaps occasional accidents in the house) until the combination is out of his system.
Best wishes
Well just woke up 1 hour ago, and all seems fine! I looked over to his crate, and there was Gizmo looking back at me with his happy eyes, and curious look.
Went out for his morning walk, and he was himself again. Playful, exploring, playing with the leaves blowing around him.
I am man enough to say it actually brought a tear to my eye seeing him like this again.
And once we got back, he ate up, and just wanted to cuddle. He seems VERY relived that it's over.
I do see some very small lumps here and there, but he is not reacting to them. It could just be the drug is still in his system, but I am hopeful that it's over.
Poor little guy !! Glad he's feeling better and hope he NEVER has to go threw that again 
I'm glad he's feeling better!
That's great news. It always feels good to see your loved pet feeling better after an ordeal like that.
Keep a watchful eye, though…you still don't know what caused all the trouble.
Oh my gosh- I have a puppy that is broken out in hives and your story sounds like the night we had! I am unnerved and so is she. What was your final outcome? My vet gave prenizone and gave her and iv drip of cortizone. We live in the Midwest and it is winter. She had a different type of food- kennel food- the night before and a piece of bacon- could this be the problem? More importantly- when will it go away?
Hi Grace,
hope your puppy is soon better.
My last Basenji once had an allergic reaction were his head was so swollen that his eyes couldn't open properly. The only thing i could pin it down to was a Pigs ear that he'd eaten the day before (i'm just wondering about the bacon?)
Fortunately it didn't happen again but i never gave him pigs ears again either.
How long did the reaction last? Without Benadryl, she is in pain, cries and goes from wild to unsettled relaxation! Thanks for your help and advice!
Poor Puppy, that sounds awful. When we had Benji i didn't know about Benadryl and the vets were closed so we waited untill the next day and everything was back to normal.
He didn't seem to be in any discomfort apart from looking a bit odd.
Grace, we are going through the same thing with one of our adults right now. If you look for my post "can you spare a thought"…you will see I posted something really similar.
Did the puppy have a vaccine in the last few days? A lot of times we see a reaction like this after a vaccine.
In our case, we don't know what triggered Hippo's reaction, and we probably never will. Lots of puppies have this once or twice, and then never again. Sometimes it takes several days before the immune system settles down. It won't hurt to continue the Benadryl for several days to get thru the discomfort.
Wow- I love this forum! THanks for your advice! I love that others have experienced the same odd symptoms- Tyllie has not had any shots for the last 3 weeks but someone did give her a piece of bacon and fed her some "kennel food" Thursday night! The vet thought it hard to believe that it could be the culprit! I am not so sure after reading the posts! I have NEVER seen welts as bad as these! She is no longer crying in pain and her appetite has somewhat returned! However, the 1/2 benadryl is given every 4-6 hrs! I will keep everyone updated on her condition- Thanks for all!
Glad Tyllies feeling a bit better Grace
Tyllie was much better after going to the vet and getting the iv drip of cortizone. I am still treating her with prenazone and benydryl. She still has a tiny bit of raised hair in the morning. It is amazing that the pre-sickness wild mouthy puppy has not returned. She is more loving and trusting and easier- loving to be cuddled. For this I am thankful!! Thanks for everyone's thoughts and advice- I was really scared to see our puppy in so much pain!! I have concluded that her reaction was due to dry skin! I have added the Halo Dreamcoat to her diet in hopes that this "mad cow" painful sickness never returns. Thanks again to all!!
Good to hear that Tyllie is feeling better..
