Snapshot A45-year-old woman with a history of systemic lupus erythematous presents to her dermatologist’s office with hives. She complains that this is the “worst it’s ever been.” She has been having episodes of itchy rashes on and off for about 6 months now. On physical exam, her entire back is covered with raised, red wheals. Some are annular. The lesions are blanching and intensely pruritic. She denies any difficulty breathing or any GI symptoms. She has a history of childhood asthma and hypothyroidism, currently on levothyroxine. The lesions usually resolve spontaneously, but this episode is particularly pruritic. She is given an anti-histamine. Introduction Pruritic inflammation of the skin commonly known as “hives” Characterized by superficial, localized edema and erythema Epidemiology most frequent dermatologic disorder seen in the emergency room Pathogenesis involving dermis and epidermis mast cell and basophil release of vasoactive substances histamine, bradykinin, and prostaglandins intense pruritus is from histamine in the dermis type I hypersensitivity reaction Timeline acute is < 6 weeks chronic is > 6 weeks Triggers of acute urticaria drugs food viral infection recent illness insect bite emotional stress cold or heat alcohol ingestion pregnancy exposure to other allergens (pet dander, dust, mold, or chemicals) sun Chronic urticarial is usually idiopathic more likely to be associated with autoimmunity Etiology identified in 40-60% of acute cases and 10-20% in chronic cases Many different types of urticarial with wide range of severity IgE-mediated chemical-induced cold-induced autoimmune Presentation Symptoms history of previous urticaria pruritus lasts a few hours resolves spontaneously Physical exam well-circumscribed erythema and edema on skin blanching, raised, and palpable wheals linear annular serpiginous can coalesce can occur anywhere on the body dermotographism (urticaria from light scratching) indicates very sensitive skin assess for angioedema of lips assess for mucosal lesions may have neutrophilic vasculitis painful as well as pruritic purpuric and hyperpigmented lesions systemic systoms such as arthralgias and GI symptoms Evaluation Labs or biopsy not indicated for acute urticaria unless diagnosis is unclear ↑ IgE For chronic or recurrent urticarial test ESR, TSH, and ANA Biopsy of lesion dermal edema lymphatic channel dilation Differential Diagnosis Hereditary angioedema Contact dermatitis Multiple insect bites Erythema multiforme Treatment If known, discontinue offending agent If concern for airway compromise epinephrine Anti-histamines second generation > first generation For urticarial vasculitis NSAIDs methotrexate colchicine dapsone Prognosis, Prevention, and Complications Prognosis most resolve spontaneously Prevention avoid known triggers take second generation anti-histamine daily Complications life-threatening angioedema neutrophilic vasculitis associated with arthritis, renal disease, and hypercomplementemia often lasts > 24 hours