Uploaded by Kazimir Schwitters


Commonly referred to as hives, is swelling of the
dermis and one of the most common skin conditions
seen in clinical practice with a prevalence of
approximately 20 percent in the general population.
Urticarial lesions are intensely pruritic,
circumscribed, raised, erythematous plaques, often
with central pallor.
Individual lesions are transient, usually disappearing
within 24 hours, not painful and resolve without
leaving residual ecchymotic marks on the skin, unless
there is trauma from scratching.
Acute urticaria — Urticaria is considered acute when it has been present for less than six weeks.
Chronic urticaria — Urticaria is considered chronic when it is recurrent, with signs and symptoms
recurring most days of the week, for six weeks or longer.
More than two-thirds of cases of new-onset urticaria prove to be self-limited. The lesions of acute and
chronic urticaria are identical in appearance, so when the problem first develops, it is not possible to
differentiate the two disorders.
A. Immune-mediated mast cell activation:
1. Type 1 hypersensitivity
• Allergen-bound IgE antibodies bind to high-affinity cell surface receptors on mast cells and basophils.
• Release of prostaglandins, leukotrienes, bradykinin, kallikrein results in vasodilation, increased vascular leak and pruritis.
2. Autoimmune:
• IgG auto-Abs bind directly to IgE receptors and induce degranulation.
B. Nonimmune-mediated mast cell activation:
• Direct nonallergic activation of mast cells by certain drugs (opioids)
• Drug-induced cyclooxygenase inhibition that activates mast cells by poorly understood mechanisms
• Activation by physical or emotional stimuli; mechanism is poorly understood but possibly involves the release of
neuropeptides that interact with mast cells
Acute urticaria most often results from type I hypersensitivity reactions, a presumptive trigger (drug, food ingestion, insect
bite or sting, infection) occasionally can be identified.
Chronic urticaria most often results from idiopathic causes and autoimmune mechanism.
Acute urticaria:
Chronic urticaria:
Insect sting or bite
Contact allergy
Transfusion reaction
Etiology identified in 40-60% of acute cases and 10-20% in chronic cases
• H1 antihistamines: mainstay, first-line choice
• H2 antihistamines
• Glucocorticoids
The approach is to treat all patients with H1 antihistamines, adding H2 antihistamines for more severe
symptoms and reserving oral glucocorticoids for those patients with prominent angioedema or persistent
symptoms despite antihistamines.