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Emergency and Acute Medicine: Urticaria
Urticaria, commonly known as hives, is a cutaneous reaction caused by activation of mast cells and basophils with release of inflammatory mediators such as histamine. This leads to increased vascular permeability, resulting in pruritic wheals and edema involving the epidermis and superficial dermis. It is more frequently seen in children, young adults, women, and individuals with atopic tendencies. Approximately 40% of patients also develop angioedema, which involves deeper dermal or submucosal tissues and may affect areas such as the lips, eyelids, or airway.
In children, urticaria is often triggered by infections or food-related reactions. Infants may present with more prominent swelling of distal extremities and even acrocyanosis, and occasionally bullae may form in the center of lesions. Acute urticaria lasts less than six weeks and is often idiopathic, although triggers such as medications (including antibiotics, opiates, and vaccines), foods, insect stings, infections (especially viral upper respiratory infections), and environmental allergens are commonly implicated. Physical triggers are also important and include dermographism (skin writing), cholinergic urticaria from heat or exercise, cold exposure, sunlight, and water contact.
Chronic urticaria persists beyond six weeks and is idiopathic in the majority of cases, though it may be associated with autoimmune diseases, immune complex disorders, or occult infections. Conditions such as Hashimoto’s thyroiditis are recognized associations. Chronic forms may also represent unrecognized physical urticaria or underlying systemic illness.
Patients typically present with intensely pruritic, well-circumscribed wheals that vary in size and shape and may appear anywhere on the body, including the palms and soles. Lesions are transient, usually resolving within a few hours, while new ones continue to appear. Associated symptoms such as fever, arthralgia, weight loss, or lymphadenopathy should raise concern for systemic disease. The presence of mucosal swelling, respiratory symptoms, hypotension, or stridor suggests progression to Anaphylaxis, which is life-threatening.
Physical examination should focus on identifying signs of systemic involvement. Airway compromise, wheezing, or hypotension must be rapidly recognized. Dermatologic findings include transient wheals, sometimes with associated edema, petechiae, or purpura. Dermographism can be elicited by lightly scratching the skin to produce a linear wheal, while other forms may require specific provocation tests such as heat, cold, or exercise challenges.
Diagnosis is clinical, based on history and examination. Acute urticaria does not require laboratory testing. In chronic cases, evaluation may include CBC, inflammatory markers, thyroid function tests, and urinalysis to assess for underlying systemic or infectious causes. A skin biopsy is reserved for suspected urticarial vasculitis, particularly when lesions are painful, prolonged, or nonblanching.
Management is primarily symptomatic and begins with removal of any identifiable trigger. The cornerstone of therapy is H1 antihistamines, preferably second-generation agents such as cetirizine or loratadine due to fewer sedative effects. First-generation antihistamines like diphenhydramine may be used as adjuncts. H2 blockers (e.g., famotidine) can be added in refractory cases. Corticosteroids are reserved for severe or persistent symptoms.
In cases with systemic involvement or airway compromise, immediate treatment with intramuscular epinephrine is essential. Bronchospasm should be treated with β-agonists such as albuterol, and hypotension managed with IV fluids and vasopressors as needed. Patients should avoid NSAIDs and opiates, as these may exacerbate symptoms.
Disposition depends on severity. Patients with stable vital signs and no airway involvement can be discharged with antihistamines and follow-up. Admission is indicated for those with anaphylaxis, respiratory compromise, hypotension, or severe refractory symptoms. Follow-up with a primary care physician or specialist is recommended, particularly for chronic urticaria lasting more than six weeks.
Important clinical considerations include the potential for a biphasic reaction in severe cases, with recurrence occurring several hours after initial resolution. Clinicians should maintain vigilance for signs of systemic disease in chronic urticaria and ensure appropriate evaluation when indicated.
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