As of 2015, the cause of chronic hives is not clear, notes Mayo Clinic. Conditions such as sunlight, insects or parasites, pressure on the skin and pain medications may trigger this skin reaction.
An allergic reaction causes the body to release histamine, a chemical produced to defend the body against infection, reports Healthline. In some people, histamine production causes symptoms of hives such as itching and swelling. Young adults are at a higher risk of chronic hives, and women are twice as likely to develop this condition as men, says Mayo Clinic.
People who develop hives should seek immediate medical attention, advises Healthline. The doctor may carry out skin tests or blood tests to determine the cause and suggest taking antihistamines.