Hives (Urticaria) are itchy and raised red eruptions of the skin. They may vary in size and blanch when pressure is applied. An individual hive may last minutes or up to 24 hours and re-occur intermittently in different sites on the body for an indefinite period of time. Hives are due to an immunologic reaction in the skin where histamine is released causing the swelling and itching. When the hives occur deeper into the skin, it causes more swelling referred to as Angioedema.
Over 20% of the population will have hives at least once in their lifetime. Acute hives may occur in any age group and is most often seen in children. These hives are often self-limited or can be controlled symptomatically with antihistamine drugs and avoidance of identifiable triggers.
Chronic hives are more common in adults and persist for more than 6 weeks with no identifiable trigger. 40% have episodes of angioedema, 45% have an autoimmune process associated with anti-thyroid antibodies or high affinity IgE receptor (FceR1) antibody.