For a child who had hives attack what is the best medicine for fever and pain.

2 separete things: For hives, as far as over the counter medications, then Diphenhydramine (benedry) can work well esp for itching. For fever and pain, if your child is above 6 mos, then Ibuprofen is best. For 2-6 mos, Acetaminophen will work. Dosing for these meds can be found online. The better question is why is you child having both of these normally separate problems, he should be evaluated by a physician.

Seek medical attn: Hives don't usually cause fever and pain, at least not in the case of acute urticaria. If she has a more complex disease (type iii hsr or urticarial vasculitis, very strange for child not on medications) she would need evaluation by a physician.