Urticaria, the medical term for hives, are itchy wheals on the skin typically caused by the release of histamine from allergy cells (Mast cells and basophils). Many patients with hives also develop angioedema, swelling of the skin or of the mucosa.
Urticaria is classified according to the duration of hives. When hives occur for less than 6 weeks, we call this acute urticaria. When hives last longer than 6 weeks, we change the classification to chronic urticaria. This helps physicians identify potential causes of urticaria which are differ based on during on hives. The chronic form is further classified in chronic spontaneous urticaria and chronic inducible urticaria. Physical urticarias are a group of conditions where hives can be induced by physical stimuli, such as heat, cold, light or pressure. In cholinergic urticaria, a common physical urticaria, an increase in core body temperature (sweating, hot showers) triggers hives. Chronic inducible hives can occur in combination with spontaneous urticaria.
Chronic spontaneous urticaria (CsU), previously called chronic idiopathic urticaria, is a very common type of chronic hives. A cause of hives is not identified in most cases of CsU. However, a large portion of patients with CsU develop autoreactive antibodies against their own allergy cells (mast cells and basophils) which lead to spontaneous release of histamine. This may last for months to years but often resolves over time.
|Spontaneous hives, angioedema or both for less than 6 weeks||Spontaneous hives, angioedema or both for more than 6 weeks|
|Acute, spontaneous urticaria (very common)||Chronic spontaneous urticaria (very common)||Chronic inducible urticaria|
|Often due to:
Symptomatic dermographism (very common)Cholinergic urticaria (common)
Cold urticaria (common)
Contact urticaria (common)
Pressure urticaria (rare)
Solar urticaria (rare)
Heat urticaria (very rare)
Vibration-induced angioedema (very rare)
Aquagenic urticaria (very rare)
Treatment of Chronic Urticaria
Treatment goals include prevention of itching, hives, swelling and avoidance of medications that have significant side effects such as corticosteroids such as prednisone. Non-sedating antihistamines are often first line therapy and “off-label” high dosages are often well tolerated and can help control itching without using other medications with that have more side effects.