My wife is on her 3rd day with a fever and today she woke up with facial edema and itching on her face. can we get a differential dx?

ANGIOEDEMA: The doctor you should be taking her to today will give you one. This is very worrisome. If her regular doctor can't see her right away an Urgent Care Center or ER is indicated for Angioedema .

You're right: many: Some sort of allergy: drug allergy, angioedema (giant hives), food allergies, contact allergic dermatitis would be at the top of the list. Other causes would include skin infection (cellulitis), conjunctivitis (inflammation of the eye) or stye, sinusitis, or tooth abscess. If it has been going on for 3 days she should be seen and evaluated. Good luck!

OK: Diff Dx: Sinusitis (likely), Facial Cellulitis, abscess,Parotid infection, salivary issues/infection, angioedma, drug allergy, allergies in general, Food allergies (MSG), thyroid disease, sequalae of underlying malignancies (lymphomas and various cancers that would cause blockage of ducts/vessels ), hypopituitarism, Sarcoid, Actinomycosis, etc. See the Dr. for a probale infection and treatment.