When a cause for hives can be found, it's most likely an infection. Viral upper respiratory infections cause about 40% of hives rashes. Fortunately, these hives outbreaks resolve as the infection resolves. A chronic bacterial infection, especially sinusitis, may be the culprit if a case of hives is lingering.
The diseases listed above are rare causes of hives, with the exception of thyroid disease. People with chronic urticaria have a higher incidence of thyroid problems compared to the general population.