Approach Considerations
Individual wheals (hives) typically clear within 24 hours without treatment; however, angioedema may take up to 72 hours to resolve. [38] Typically, the hives (urticarial lesions) do not remain after the symptoms resolve. Excoriation may be present due to scratching of the lesions. With acute urticaria, wheals can recur for up to 6 weeks, depending on the cause. For chronic urticaria, urticarial flare-ups reoccur more days than not, for more than 6 weeks.
Timely transport to the ED for any patient with signs or symptoms of a life-threatening allergic reaction, including urticaria (hives), angioedema, or anaphylactic shock is essential. Acute urticaria may progress to life-threatening angioedema and/or anaphylactic shock in a very short period, although anaphylaxis usually presents as rapid-onset shock with no urticaria or angioedema. [5] See Anaphylaxis.
If associated angioedema is present, especially if laryngeal angioedema (eg, hoarseness, stridor) is suspected, prehospital administration of 0.3-0.5 mg of intramuscular epinephrine may be warranted.
If associated bronchospasm is present, prehospital nebulized albuterol may be warranted.
Other measures may be appropriate, such as continuous ECG, blood pressure and pulse oximetry monitoring; administering intravenous crystalloids if the patient is hypotensive; and administering oxygen.
Diphenhydramine (25 mg IV or 50 mg IM or PO) or hydroxyzine (50 mg IM or PO) should be administered if they are available. [6]
The management of urticaria is straightforward and typically is not altered by underlying etiology, but guidelines are in evolution with some variation in different parts of the world. [39, 40, 41]
Antihistamines are first-line therapy for urticaria. The older sedating antihistamines (first-generation antihistamines) that block the H1 receptors were previously first-line therapy for urticaria. [6, 7] Diphenhydramine and hydroxyzine are the most commonly used in this class. They act more rapidly than the minimally sedating H1-blocking antihistamines and are effective in relieving the pruritus (itchiness) and rash in most cases. However, because these medications are often sedating with the potential for other anticholinergic adverse effects, second-generation antihistamines are now considered first line. [8, 32, 42, 43]
Newer H1-blocking, minimally sedating, second-generation antihistamines are now available and include fexofenadine, loratadine, desloratadine, cetirizine, and levocetirizine. These are now considered first line and are used in the management of both acute and chronic urticaria. [43, 44] If symptoms are uncontrolled, the dose can be increased up to four-fold. In fact, up-dosing has been shown to increase the response rate without increasing the adverse effect profile. [32] If symptoms are still uncontrolled, a first-generation antihistamine can be added.
H2 antihistamines, such as cimetidine, famotidine, and ranitidine, may have a role when used in combination with H1 antihistamines in urticaria. H1 and H2 antihistamines are thought to have a synergistic effect that may result in a more rapid and complete resolution of urticaria than H1 antihistamines alone. [45] Cimetidine, in particular, is thought to effect cytochrome P450 enzymes involved in the metabolism of first-generation antihistamines, thus increasing their plasma concentrations. [32] Because of this, H2 antihistamines are often added in combination with H1 antihistamines in the treatment of acute and chronic urticaria. However, the evidence supporting the use of H2 antihistamines in combination with H1 antihistamines is weak and does not seem to show any advantage over use of H1 antihistamines alone. Thus, their addition is often physician dependent. [36, 32, 43, 46]
Doxepin is an antidepressant and an antihistamine that blocks both H1 and H2 receptors and may be effective in refractory cases of urticaria in doses of 25-50 mg at bedtime or 10-25 mg 3-4 times a day. [47]
Glucocorticoids stabilize mast cell membranes and inhibit further histamine release. They also reduce the inflammatory effect of histamine and other mediators. Oral glucocorticoids are effective in acute urticaria but are not suitable for long-term use. In one study, acute urticaria improved more quickly in the group treated with prednisone than in the group treated with placebo. [48] In adults, 40-60 mg daily of prednisone for 5 days is a reasonable therapeutic regimen. In children, the treatment is 1 mg/kg/d for 5 days. Tapering of the corticosteroid dose is not necessary in most cases of acute urticaria. [1]
If urticaria is present with angioedema and systemic symptoms such as coughing or wheezing are present, raising concern for anaphylaxis, [8] 0.3-0.5 mg of epinephrine should be administered intramuscularly. Remember that ACE-inhibitor–induced angioedema usually does not respond to epinephrine or most other common therapies, since it is not an IgE-mediated process. [49]
The use of methotrexate, colchicine, dapsone, indomethacin, and hydroxychloroquine may be effective in the management of urticarial vasculitis. [9]
Control of chronic urticaria may be achieved with omalizumab, although anaphylaxis and angioedema are potential risks. [50, 51, 52] Combined therapy with antihistamines or an immunosuppressive agent may be required. [53, 54, 55, 56, 57, 58]
Topical therapy with 5% doxepin cream (Zonalon) or capsaicin may also be used in refractory cases.
Patients with chronic or recurrent urticaria should be referred to a dermatologist or allergist for further evaluation and management.
Inpatient care
In general, patients with urticaria (hives) can be cared for on an outpatient basis unless their urticaria is severe and does not respond to antihistamine therapy or if they progress to laryngeal angioedema and/or anaphylactic shock, or have comorbidities that require inpatient therapy.
Consultations
Consultation with or referral to a dermatologist, allergist, immunologist, or rheumatologist may be appropriate in selected cases, particularly in cases of complicated, recurrent, refractory, severe, or chronic urticaria. Dermatology referral is mandatory if urticarial vasculitis is suspected.
Prevention of Urticaria
Patients with acute urticaria should avoid any medication, food, or other allergen that has precipitated urticaria (hives) or other serious allergic reaction previously. Chronic urticaria is seldom related to food allergens, and complicated elimination diets are seldom of benefit. [59] Urticaria is not contagious, unless the swollen hives themselves contain a pathogen.
Long-Term Monitoring
Most patients with urticaria can be treated at home with first- or second-generation H1 antihistamines alone or in combination with one another (ie, cetirizine uptitrated to 20 mg twice daily, diphenhydramine 50 mg q6h or hydroxyzine 50 mg q6h for 24-48 h) In refractory cases, oral glucocorticoids can be added. Additional therapies likely warrant referral to a specialist.
If the patient has angioedema that is treated successfully in the ED, the patient should be sent home with an EpiPen prescription and told to keep it with him or her at all times and to use it if swelling of the lips, tongue, face develops or if his or her voice acutely become hoarse.
Consultation with or referral to a dermatologist, allergist, immunologist, or rheumatologist may be appropriate in cases of suspected urticarial vasculitis and in cases of chronic or recurrent urticaria.
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Urticaria developed after bites from an imported fire ant.
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Urticaria associated with a drug reaction.
