My boxer, Bella age 5, has a cancerous mast cell tumor.  She hasn't been able to have it removed yet because her blood platelet count is extremely low and therefore, surgery isn't safe (blood won't clot for surgery).  So we took her to a specialist and paid over 1K in hopes they could tell us WHY and what's happening.  No answer.. all her tests are normal.  Ugh!! 

Bella is on Doxycycline, Benadryl and Pepcid.  Saturday morning her face was swollen and eyes almost shut.  Got a steroid injection and benadryl injection.  Dr said take her off everything except Benadryl and Pepcid.  Monday morning her face was covered in Hives.  Dr prescribed Prednisone steroid meds and said to give all 4 medications Monday night so we did.  About an hour later her legs and head are covered in Hives again!  So here we are.. it's 12:30am Tuesday morning and I'm sitting with her and watching to make sure it doesn't get worse.  I called the emergency line and they said if it's not getting worse, to call tmrw morning to let vet know.

Mast cell tumors can release toxic granules which can cause hives.  Buut not sure if this is what is happening or is she allergic to a medication??  Anyone have a similar case of their Boxer with a mast cell tumor and hives?  The mast cell tumor is on her hind and the hives are on her head, neck and legs.