Hives may be the first sign of life-threatening anaphylaxis. If so, it will be followed by agitation, wheezing due to the blockage of the airway, numbness, palpitations, cold sweats and or low blood pressure. Without prompt treatment, coma and cardiac arrest can occur. Prognosis Unpredictable, depending on the cause. If a medication or acute viral infection is responsible, hives usually disappear within hours or days.
Some cases become chronic and last for months or years.
Most eventually go into spontaneous remission even if the cause in not identified.