Chronic Spontaneous Urticaria (CSU)
Chronic spontaneous urticaria, or CSU, is the medical term for chronic hives that have no known cause.
It can look and feel different for everyone, but all cases of CSU result in itchy hives that last for six weeks or longer. This can result in raised red bumps that may grow, spread, change, disappear and reappear on the skin. It is also sometimes referred to as chronic idiopathic urticaria, or CIU.
Unlike other types of hives, there is no known trigger of CSU. This makes it harder to diagnose and treat than other conditions, and it may take some time before you are diagnosed. If you think you might have CSU, speak with your provider who will diagnose CSU by ruling out other potential causes, such as an infection or allergic reaction.