Hives also called ‘urticaria’ is a rash that is characterized by red, raised, itchy swelling of the skin that wax and wane. Generally, a single lesion does not last more than a couple hours. Though it is commonly a result of allergy, there are many non-allergic causes.
When the rash is a result of an allergy, it is considered a systemic reaction involving the whole body. The significance of this is that subsequent allergic reactions may be more violent and lead to a life threatening condition. Therefore it is important to identify the etiology of this allergic reaction with your physician to help avoid future reactions.
The non-allergic causes are numerous and could be a result of mild condition to more severe systemic illnesses. These conditions include underlying Rheumatologic, Infectious, Endocrine, Hematologic and Autoimmune diseases. The treatment of these underlying conditions generally leads to resolution of the urticarial rash.