I've been taking antihistamines for 4 years and I'm off them now for 48 hours for an appointment. What are the withdrawals for fexofenadine and cetriz?

Not much. Female on antihistamines for 4 years, now suddenly off and wants to know withdrawal symptoms. There should not be any withdrawal symptoms from stopping antihistamines. If you were taking antihistamines for allergy symptoms, your allergy symptoms will probably return.
Few problems. they don't usually cause withdrawals. at most whatever condition you are taking them for could bounce back with a vengeance, but that is not likely.