Urticaria
Urticaria is transient, pruritic, edematous wheals from mast cell histamine release, classified by duration into acute (under 6 weeks) and chronic (6 weeks or longer, usually spontaneous/idiopathic). Diagnosis is clinical with minimal testing, and treatment is stepwise second-generation H1 antihistamines up-titrated as needed, adding omalizumab for refractory chronic disease.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Definition: urticaria is a mast-cell-driven skin reaction producing transient, pruritic, edematous wheals (hives), often with accompanying angioedema.
- Epidemiology
Common: a large fraction of people experience urticaria at some point.
- Risk factors
Recent infection: the most common trigger of acute urticaria, especially viral.
- Pathophysiology
Mast cell mediator release: histamine and other mediators increase dermal vascular permeability, producing wheals and pruritus.
- Clinical features
Wheals: raised, erythematous or pale, intensely pruritic lesions with surrounding flare.
- Differential diagnosis
Urticarial vasculitis: individual lesions lasting more than 24 hours, painful or burning, resolving with bruising, unlike ordinary wheals that clear without residual marks; needs biopsy (Angioedema may coexist).
- Diagnosis
Diagnose clinically by lesion morphology and duration, with minimal testing: urticaria is a clinical diagnosis defined by transient pruritic wheals each lasting under 24 hours, subclassified as acute…
- Management
First-line, a second-generation H1 antihistamine at standard dose: for example cetirizine 10 mg PO daily, continued regularly rather than as needed.
- Complications
Impaired quality of life: sleep disruption and daily discomfort in chronic disease.
- Prognosis
Acute urticaria: self-limited, resolving within days to weeks.
- Prevention
Avoid identified triggers: culprit drugs (NSAIDs, opioids) and the relevant physical stimulus in inducible urticaria.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Angioedema
Angioedema is self-limited, non-pitting swelling of the deep dermis and submucosa that follows one of two mechanisms: mast cell (histamine) mediated, which occurs with urticaria and responds to epinephrine and antihistamines, or bradykinin mediated, which occurs without urticaria and does not. Distinguishing the two determines whether treatment is allergic therapy or bradykinin-targeted therapy, and airway involvement is the central danger.
- Anaphylaxis
Anaphylaxis is an acute, potentially fatal systemic hypersensitivity reaction from massive mast cell and basophil mediator release, presenting within minutes as skin, respiratory, cardiovascular, and gastrointestinal involvement after allergen exposure. It is a clinical, treat-first diagnosis, and intramuscular epinephrine is the immediate life-saving therapy.