Breakout in hives, aural hematoma and difficulty defecating in 8 year old GSP dog

A couple weeks ago we noticed our dog was excessively grooming the inside of her thigh until it was red. It appears as though it could’ve been a rash so we’ve been applying some ointment pretty regularly to help her. Yesterday, I noticed large hematoma on both ears and more hives of similar degree on the base of the nose, gums, and on the ear flaps. It seems to be progressing into a serious infection or allergic reaction im not sure. She hasn’t been able to defecate for about a day and a half. Eats decently but is not drinking much water. Just now we’re starting to notice she’s having some minor difficulty breathing. Vomiting has also occurred. She is going to the vet first thing in the morning but god im worried about her. I cant stop thinking about it. If it’s an allergic reaction could it progress even more overnight? Could it be life threatening?