Urticaria

Urticaria: Excerpt from The 5-Minute Pediatric Consult

Christopher P. Raab, MD

Urticaria - BASICS

Urticaria - description

• Urticaria is best described as raised, pruritic circumscribed erythematous papules.
• Single lesions may coalesce as they enlarge, forming generalized raised erythematous areas, and are transient, typically lasting several hours.
• Also known as “hives” or “nettlerash”
• Acute: <6 weeks duration
• Chronic: >6 weeks duration
• Other similar but non-urticarial entities:
  • Angioedema: Urticarial lesion that forms in the deep dermal, SC, and submucosal layers
  • Anaphylaxis: Hypersensitivity reaction after exposure to an antigen, producing weakness, respiratory compromise secondary to airway edema, urticarial rash, pruritus, and hypotension; can lead to shock

Urticaria - general prevention

When a trigger is identified, avoidance is the main preventive measure.

Urticaria - epidemiology

• Female:Male ratio of 3:2
• No variation in race

Urticaria - incidence

Lifetime incidence of 15–25%

Urticaria - pathophysiology

• Immune-mediated:
  • Antigen is cross-linked to IgE on a mast cell.
  • This causes mast cell activation leading to the release of vasoactive mediators, such as histamine, leukotrienes, prostaglandin D2, platelet-activating factor, and other vasoactive mediators.
  • These vasoactive mediators cause pruritus, vasodilatation, and capillary leak, which lead to the characteristic findings.
  • Common triggers include some medications such as penicillins, foods such as milk or eggs, and envenomations.
• Non–immune-mediated:
  • Degranulation of mast cells secondary to other non-IgE reactions such as physical changes, chemicals, some medications such as beta-lactams and sulfa-containing drugs and some foods
• Autoimmune-mediated:
  • Degranulation of mast cells caused by cross-linking of IgE by IgG, or IgG binding to the high-affinity IgE (FcεRI) receptor on mast cells

Urticaria - etiology

Acute Urticaria

• Viral infections are thought to make up ~80% of all cases of acute urticaria. Most commonly isolated causes include the following viruses:
  • Epstein–Barr
  • Coxsackie A and B
  • Hepatitis A, B, and C
• Parasitic infections
• Bacterial infections (especially group A Strep)
• Medications: Most frequently reported include the following:
  • NSAIDS
  • Opiates
  • Vancomycin
• Radiocontrast
• Foods
• Transfusion of blood products
• Food additives and dyes
• Natural remedies including cranberry, feverfew, glucosamine, and ginger
• Insect venom including bees, wasps, hornets

Chronic Urticaria

• Idiopathic: Majority have unknown cause, but many feel that an association with an autoimmune mechanism is likely
• Physical (~20–30%):
  • Dermatographism (9%): Stroking of skin causes linear urticaria at site of contact.
  • Cholinergic (5%): Diffuse erythema and elevated but pale urticarial lesions; intense pruritus. Associated with sweating reflex, so often associated with overheating or exertion. May be worsened in combination with other triggers in specific combinations
  • Cold (3%): Urticarial lesions present at areas of skin exposed to low temperatures; has a familial and nonhereditary form
  • Delayed pressure/vibratory: Deep or prolonged pressure on skin produces significant urticaria and often angioedema. Vibratory urticaria is a form of delayed pressure urticaria caused by repetitive vibration (e.g., use of a jack-hammer).
• Mast cell disease:
  • Urticaria pigmentosa: Excessive number of mast cells in skin, bone marrow, lymph nodes, and other tissues. Flares characterized by pruritus, flushing, tachycardia, nausea, and vomiting
  • Systemic mastocytosis
• Systemic disease:
  • Rheumatologic:
    • Urticarial vasculitis: Erythematous wheals that resemble urticaria but histologically appear as leukocytoclastic vasculitis. Often presents with systemic symptoms and lasts for >24 hours
    • Muckle–Wells syndrome: Chronic recurrent urticaria, deafness, amyloidosis, and arthritis
  • Neoplasms
  • Infections: Parasites especially noted to cause chronic urticaria
  • Autoimmune: Antibodies to IgE or IgE receptor (FcεRI)

Urticaria - DIAGNOSIS

Urticaria - signs & symptoms

Urticaria - history

• Description of rash. Lesions may not be present at time of exam due to transient nature. Digital photos are often useful.
• Duration of symptoms, acute versus chronic:
  • If acute (<6 weeks) ask about:
    • Viral symptoms including rhinorrhea, cough, fever, etc.
    • Any medications (prescription or over-the-counter), or any herbal remedies
    • Any new foods or beverages
    • Any new exposures to perfumes, chemicals, etc.
  • If chronic (>6 weeks):
    • History of previous episodes including timing, exposures, any past history of urticaria or angioedema
    • Other symptoms or variations in presentation
    • Symptoms of systemic diseases, such as hyperthyroidism, systemic lupus erythematosus [SLE], rheumatoid arthritis, polymyositis, amyloidosis, infections, and lymphoma
    • Duration of lesions

Urticaria - physical exam

• Appearance of rash: Has classic wheal and flare appearance
• Respiratory: Look for evidence of stridor, wheezing, or dyspnea. If present, be concerned for airway compromise or lower airway edema from an anaphylactic reaction.
• Facial or neck swelling: A concern for possible airway compromise
• A full physical exam should be performed to look for signs of systemic disease or malignancy, for example:
  • Upper respiratory infections
  • Thyromegaly
  • Lymphadenopathy or splenomegaly that suggests lymphoma
  • Joint examination for any evidence of connective tissue disease, rheumatoid arthritis, or SLE

Urticaria - tests

Urticaria - lab

• Testing is often fruitless unless indicated by history and physical examination.
• Skin testing may be performed if causative agent is thought to be one of several food items.
• If symptoms are difficult to handle, or persist beyond 3 months, consider:
  • CBC with differential
  • ESR
  • Thyroid studies (thyroid-stimulating hormone [TSH], free T4, antithyroglobulin, and antiperoxisomal antibody)
• If symptoms are atypical, last >1 year, or are suggestive of urticarial vasculitis:
  • Complement studies
  • ANA titer
  • Liver function tests
  • Skin punch biopsy

Urticaria - differencial diagnosis

• Viral exanthema
• Atopic dermatitis
• Contact dermatitis
• Insect bites
• Maculopapular drug rash
• Erythema multiforme
• Plant-induced eruptions
• Henoch–Schönlein purpura
• SLE

Urticaria - TREATMENT

Emergent Treatment

If any difficulty breathing, stridor or wheezing, or other signs of anaphylaxis, give epinephrine 0.01 mL/kg of the 1:1,000 solution SC/IM

Urticaria - medication

Acute urticaria: Usually self-resolving but can treat with diphenhydramine 1 mg/kg/dose or total 5 mg/kg/d divided q6h or hydroxyzine 2 mg/kg/d divided q6h for pruritus.

Urticaria - first line

• H1 antagonists:
  • 1st-generation antihistamines may be more effective than 2nd generation, but are more sedating:
    • Diphenhydramine (Benadryl): 5 mg/kg/d divided q6h
    • Hydroxyzine (Atarax): 0.6 mg/kg/dose q6h
    • Cyproheptadine (Periactin): 2 mg up to 3 times a day: Primary treatment for cold urticaria
  • 2nd-generation antihistamines are less sedating, longer acting but often not as effective:
    • Cetirizine (Zyrtec): Dosing varies by age from 2.5–10 mg daily
    • Loratidine (Claritin): 5 mg daily
    • Fexofendine (Allergra): Not indicated for <6 years of age; >6 years of age can use 30 mg b.i.d.

Urticaria - second line

H2 antagonists: Added as second agent as skin cells have both H1 and H2 receptors and a synergistic effect can be achieved by addition of H2 blocker

• Ranitidine (Zantac): 2–4 mg/kg/d divided b.i.d.

Urticaria - third line

• Increase second-generation H1 antagonist dose to maximum for age
• Combined H1 and H2 antagonist
  • Doxepin (Sinequin): A tricyclic antidepressant. >12 year 10–50 mg/d and can slowly titer up to 100 mg/d. Potent antihistamine but poorly tolerated due to sedation, hypotension, anticholinergic side effects, and massive weight gain
• Leukotriene inhibitors: Minimal additive response noted in clinical studies
  • Montelukast (Singulair): 5 mg daily

Urticaria - fourth line

• Corticosteroids: Titer to lowest effective dose. Start with standard dose of 0.5–1 mg/kg/d of prednisone. Often poorly tolerated secondary to substantial side effects including hypertension, immunosuppression, hyperglycemia, physical changes
• Other nonstandard therapies have been tried in small case studies: Cyclosporine, colchicines, dapsone, IV immunoglobulin (IVIG), plasmapheresis, methotrexate, cyclophosphamide, calcium-channel blockers, ephedrine

Urticaria - FOLLOW UP

Urticaria - prognosis

Chronic urticaria:

• Resolution in 50% by 12 months
• Another 20% resolve by 5 years
• 10–20% >20 years; many of those who continue to have symptoms are felt to associated with the autoimmune etiology
• May have recurrences; physical urticaria subtypes more likely to recur

Urticaria - complications

Anaphylaxis with resulting edema of the upper airway is the major life-threatening complication. The patient should seek immediate medical attention.

Urticaria - patient monitoring

• Watch for signs and symptoms of anaphylaxis, as this is the major complication.
• Patients with chronic urticaria should follow-up with their physician on a regular basis to monitor symptoms and response to therapies.

Urticaria - bibliography

1. Dibbern D, Dreskin S. Urticaria and angioedema: An overview. Immunol Allergy Clin N Am. 2004;24(2):141–162.
2. Dibbern D. Urticaria: Selected highlights and recent advances. Med Clin N Am. 2006;90(1):187–209.
Leung DYM. Urticaria and angioedema (hives). In: Behrman RE, Kliegman RM, Jenson HB. Nelson Textbook of Pediatrics. 17th ed. Philadelphia: WB Saunders; 2004:778–780.
3. Sheikh J. Advances in the treatment of chronic urticaria. Immunol Allergy Clin N Am. 2004;24(2):317–334.

Urticaria - CODES

Urticaria - icd9

708.9 Urticaria, unspecified

Urticaria - FAQ

• Q: When should I refer patients to a specialist and to what specialty should I send them?
• A: Often referral is made when a trigger cannot be identified, or if it is felt to be a food or medication trigger and/or the symptoms persist for >6 weeks. Refer to a dermatologist or allergist–immunologist experienced in the evaluation and work-up of urticaria.
• Q: When should treatment with corticosteroids or other nonstandard therapies be used to treat chronic urticaria?
• A: Typically, these medications carry significant side effects and should be reserved for those patients in whom the urticaria is causing significant alterations in activities of daily living.
• Q: When does a patient need to be hospitalized or observed during an episode of urticaria?
• A: Concerning signs include extensive angioedema, respiratory symptoms such as stridor or wheezing, or nausea/vomiting. Symptoms of anaphylaxis should be treated with epinephrine and the patient observed for several hours to ensure that symptoms do not recur.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Angioedema

• Back to disease: Angioedema: Introduction
• Next Book Extract About Angioedema: Surveys relating to Angioedema
• More Book Extracts: All Online Books for Angioedema

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

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