some facts about urticaria

Urticaria is commonly referred to as nettle rash; hives; wheals, is the most frequent dermatologic disorder seen in the Emergency Depaatment. It's clinical manifestasions appears as raised, very pruritic, well-circumscribed areas of erythema and edema involving the dermis and epidermis. Urticaria may be lasting less than 6 weeks (acute type) or lasting more than 6 weeks (chronic type). There are some variety of urticaria variants exist, including acute immunoglobulin E (IgE)–mediated urticaria, chemical-induced urticaria (non-IgE-mediated), cholinergic urticaria, urticarial vasculitis, autoimmune urticaria, cold urticaria, mastocytosis, Muckle-Wells syndrome, and many others.

Acute IgE-mediated urticaria is the most benign form of anaphylaxis. It usually occurs independently, but it may be accompanied by the more serious clinical manifestations of anaphylaxis, angioedema, and anaphylactic shock. The etiology of both acute and chronic urticaria are numerous (see Causes below). The etiologic agent is more likely to be identified in acute urticaria (40-60%) than in chronic urticaria (10-20%). The lesions of IgE-medicated urticaria usually last less than 24 hours and are often migratory, leaving no residual skin abnormalities. The lesions of urticarial vasculitis usually last longer than 24 hours, are both painful and pruritic, and often leave purpuric and hyperpigmented lesions.

Clinical Presentation :

1. Edematous papules and plaques, discrete or confluent
2. Localized, regional, or widespread
3. Individual lesions disappear in hours
4. Lesions are intensely pruritic

Histopathology :

1. Perivascular infiltrate of neutrophils and eosinophils early
2. Lymphocytes perivascular, neutrophils, and eosinophils interstitial later
3. Sparse perivascular infiltrate of lymphocytes and a few

Pathophysiology:
Different causes lead to degranulation of mast cells,which attract inflammatory cells and cause vasodilation and edema in the dermis.