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.