Urticaria (Hives) is a topic covered in the 5-Minute Pediatric Consult.

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Basics

Description

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

Epidemiology

  • Female-to-male ratio of 3:2
  • No variation in race

Incidence

Lifetime incidence of 15–25%

General Prevention

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

Pathophysiology

  • Immune mediated
    • Antigen is cross-linked to IgE on a mast cell.
    • This event 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 β-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

Etiology

  • Acute urticaria
    • Viral infections are thought to make up approximately 80% of all cases of acute urticaria in children. Most commonly isolated causes include the following viruses:
      • Picornavirus
      • Coronavirus
      • Epstein-Barr
      • Hepatitis A, B, and C
    • Parasitic infections
    • Bacterial infections (especially group A strep)
    • Medications: most frequently reported include the following:
      • NSAIDs
      • Opiates
      • β-lactams
      • 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: Most have an unknown cause, but many feel that an association with an autoimmune mechanism is likely.
    • Physical (~20–30%)
      • Dermatographism (9%): Stroking of skin using mild-to-moderate pressure with fingernail or hard object 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; familial and nonhereditary forms
      • Aquagenic: Urticarial lesions arise when the patient is exposed to water (e.g., bathtub, swimming pool).
      • 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 jackhammer).
    • 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 >24 hours
        • Cryopyrin-associated periodic syndromes can present with urticaria, such as 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)
      • Hashimoto disease, hypothyroidism

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Citation

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TY - ELEC T1 - Urticaria (Hives) ID - 617061 ED - Cabana,Michael D, BT - 5-Minute Pediatric Consult UR - https://peds.unboundmedicine.com/pedscentral/view/5-Minute-Pediatric-Consult/617061/all/Urticaria__Hives_ PB - Wolters Kluwer ET - 8 DB - Pediatrics Central DP - Unbound Medicine ER -