Urticaria

Presentation

Urticaria or hives is a rash often preceded by itching that can occur on any part of the body. The lesions are raised, pinkish-white patches/plaques, classically called wheals. They typically are well circumscribed but may be coalescent, and may have central pallor. They are blanchable and pruritic. Eruptions may evolve quickly over minutes to hours. They will typically last less than 24 hours, but may last for days or weeks

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https://en.wikipedia.org/wiki/Hives

Epidemiology

Approximately 20% of the population has experienced an episode of hives, and it can occur in any age population. Chronic urticaria, or the presence of hives on most days of the week for more than 6 weeks, has a prevalence of approximately 1%.

Pathogenesis

Urticaria is edema of the stratum corneum related to vascular dilatation and increased capillary permeability. Angioedema is caused by a similar mechanism but involves the dermis and subcutaneous tissue. The edema is non-pitting. Angioedema commonly affects the gastrointestinal tract, upper respiratory tract, and the tissues around the eyes and lips. Angioedema may progress to respiratory tract involvement, and therefore must be monitored closely as it may be life threatening.

The end result of histamine release can be triggered by multiple mechanisms. IgE on mast cells binding to antigens results in mast cell degranulation and histamine release. Histamine can also be released by activation of the complement system, plasma kinin formation, or physical forces. Histamine increases capillary permeability and causes vascular dilatation resulting in edema, and histamine also causes pruritis. 

Common Causes of Urticaria

  1. Idiopathic -85% of cases no etiology is identified.
  2. Allergic
    1. Antibiotics- Penicillin, Cephalasporins, Sulfas. May occur during or after completion of taking drug. May take weeks to resolve.
    2. Bee stings may cause local reaction
    3. Inhalants- animal dander, pollen, feathers
    4. Contact
    5. Food- milk, egg whites, peanuts, shellfish, and fish
    6. Mosquito and flea bites
  3. Non-allergic
    1. Stress
    2. Viral infections- hepatitis, EBV
    3. Dermatographia
    4. Heat and cold- usually to exposed area only like after putting on ice pack to an area
    5. Sun exposure
    6. Pressure- around area of tight clothes
    7. Vibration
    8. Aquagenics
  4. Hereditary Angioedema. Autosomal dominant and there is a deficiency of C1q esterase inhibitor which leads to higheer levels of activated complement.
  5. Associated with systemic diseases- SLE, ALL, Lymphoma, endocrinopathies
  6. Urticaria pigmentosa- Darier's sign.  Rubbing of the pigmented lesion will lead to wheal formation.

Differential Diagnosis

1. Viral exanthems (fifth disease, roseola, rubeola, rubella, enterovirus) – typically non-pruritic. Typically persists for days, associated with fever and rash

2.  Auriculotemporal syndrome – nonpruritic flushing over the cheeks or jawline after eating

3.  Sweets syndrome – painful, inflammatory papules and plaques associated with fever and arthralgia

4.  Atopic dermatitis – papules, scaling, pruritic. Face, scalp, extremities in younger children; flexural surface as child grows old

5. Contact dermatitis – history of direct skin exposure to an irritant. Often there is vesciculation.

6.   Erythema multiforme – erythematous, iris shaped macules with targetoid apperance

7.  Bullous pemphigoid – evidence of tense blisters

8.  Insect bites – individual lesions that persists for days, but can also cause systemic urticaria

Evaluation

  1. History with emphasis on drugs, diet, and previous bouts of hives
  2. Have patient or family keep a diary of when hives occur and what medications were taken, foods eaten, and activities.
  3. No further workup necessary unless suspect underlying systemic disease. 

Treatment

  1. Avoidance of specific drug, food, or activity
  2. If there is a severe reaction or angioedema of the airway, may use epinephrine(1:1000) The dose is 0.01ml/kg.with maximum of 0.3ml. 
  3. Antihistamines- Atarax, Benadryl,Tavist, Claritin
  4. In rare instances, systemic steroids may be useful.
  5. Compassion and reassurance 

References

  1. Eitches, Robert. Urticaria: A wheal of misfortune. Contemporary Pediatrics. June 1993.
  2. Weston WL. Urticaria. Pediatrics in Review. 1998; 19:240-244.
  3. Plumb J, et al. Exposures and Outcomes of Children with Urticaria Seen in a Pediatric Practice-Based Research Network.  Archives of Pediatrics and Adolescent Medicine. Sept. 2001
  4. Leickly F. When the road gets bumpy: Managing chronic urticaria. Contmeporary Pediaatirics May 2000
  5. Alangari A. .Clinical Feataures of Children with Cold Urticaria Pediatrics 2004 April e-313
  6. Sacksen C. et al. The Etiology of Different forms of Urticaria in Childhood.  Pediatr Dermatol. 2004; 21(2) 102
  7. Hernandez R, Cohen B.Insect Bite Induced Hypersensitivity and The SCRATCH Principles: A New Approach to Papular Urticaria.  Pediatrics 2006;118 e189-196
  8. Sardina N, Craig T.  Recent Advances in Management and Treatment of Hereditary Angioedema.  Pediatrics December 2011

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