Swollen lips & blisters since 5:45am, saw hospital was given antihistamines and steroids, told possible food allergy. swelling returned it now 10:32pm?

Allergic reaction: When people are treated in an emergency room for a condition, and that condition returns or worsens, they generally would want you to call them or go back for evaluation. Respiratory distress, difficulty swallowing and progressive facial swelling can indicate severe allergic reaction known as anaphylaxis and requires emergent care and possibly transport by ambulance!

Airway?: Keep in mind the half life of your antihistamine. It is probably wearing off and needs to be redosed. If not improving within an hour of redosing you need to go back to the ER. Cetirizine 10mg will last 24 hours.