What causes a break out of hives all over? getting hives 4 weeks. on arms, thighs, hands and feet. maybe 25 of them total.

? acute urticaria: as you don't a cause for as related to any food or medicine, it could be just acute urticaria, common, and most probably due to a virus, will go on its own, antihistamines would help control the symptoms. If symptoms progress, you develop lip / tongue swelling, difficult breathing, or hives stay more than 6 weeks, see your doctor, who may refer you to a dermatologist or an allergist, best wishes