Do hives from food allergies always mean anaphylactic reaction?

Not always. Hives as a symptom along the continuium of allergic reactions. The concern is that the next time they are exposed to this allergen they may react more severely (anaphylaxis). This is definitely something you want to see your child's doctor about.
Not always. Anaphylaxis involves multiple organ system involvement. Having hives locally may not constitute anaphylaxis, however, if you are breaking out all over your body, with other symptoms, then it is anaphylaxis.