Hi.. Thanks for the query.. Hives on the body can be commonly due to Allergic reaction.. Common allergens can be insect or bug bits, bed bugs, food allergies, skin cosmetic, detergents, soaps etc.. So first of all you should consult an Emergency room and get evaluated.. A blood test can be done to rule out the exact cause of the symptoms.. Meanwhile you can take antiallergic medication like Benadryl or Levocetrizine etc to reduce the hives.. Do cool compresses over the hives.. If there is itching avoid scratching to avoid Infection.. A steroid shot can be given if symptoms are severe.. Hope this helps. Regards.