My daughter (30 months now) developed an allergy to strawberries and had symptoms exactly as you describe. She suddenly became allergic to them about 6 months ago and broke out in hives, vomited, but played and acted normal. Don't discount things that have been around. Try removing a couple of common allergens for a few days and see if the hives go away..."Although an individual could be allergic to any food, such as fruits, vegetables, and meats, there are eight foods that account for 90% of all food-allergic reactions. These are: milk, egg, peanut, tree nut (walnut, cashew, etc.), fish, shellfish, soy, and wheat." Write down everything your daughter eats and if you notice the hives getting worse/more appearing/fading to try to rule out the culprit. Out daughter vomited two mornings in a row within 2 hours of having strawberries. Hope you can figure it out because Drs rarely do without the vigilance of the parents.