How long does it take for an allergic reaction like hives to show up after eating something?

Not very long. With food allergies hives either alone or as the first symptom of a more serious life-endangering condition called anaphylaxis typically appear within 5 minutes to 2 hours after the first bite. When appearing in a few minutes hives usually appear around the lips, eyes, face & neck. When 1st appearing after 2 hours hives can appear anywhere. Hives may be delayed as long as 8-12 hours after eating.
Minutes to hours. Reactions to foods usually occur quickly...Within minutes to hours. It would be very unusual (? Almost never)to show up a day or more later.