dermatologic disorders
Urticaria
Etiology of Urticaria
Urticaria is classified as acute (<6 weeks) or chronic (>6 weeks); acute cases (70%) are more common than chronic (30%). Acute urticaria(see table) most often results from Type I hypersensitivity reactions A presumptive trigger (eg, medication, food ingestion, insect bite or sting, infection) occasionally can be identified. Chronic urticariamost often results from Idiopathic causes Autoimmune disorders Chronic urticaria often lasts months to years, eventually resolving without a cause being found. Urticarial lesions (wheals or hives) are migratory, elevated, pruritic, reddish plaques caused by local dermal edema. Photo provided by Thomas Habif, MD. This photo shows a positive ice cube test in a patient with idiopathic cold-induced urticaria. This photo was taken 5 minutes after the ice cube was removed. © Springer Science+Business Media Urticaria pigmentosa may manifest as reddish plaque-like lesions on the skin. © Springer Science+Business Media Systemic mastocytosis can cause yellowish tan to reddish brown macules and papules. © Springer Science+Business Media This photo shows reddish brown macules on the back of a school-aged child. © Springer Science+Business Media The infant shown here has profuse papulonodular and plaque lesions of urticaria pigmentosa. © Springer Science+Business Media This photo shows solar urticaria in a woman who had been wearing a tank top. These hives appear within minutes of sun exposure. © Springer Science+Business Media Dermatographism, or skin-writing, may occur when the skin is lightly scratched and results in raised red lines. © Springer Science+Business Media 