See also

Anaphylaxis

Key Points

1. There are many causes for urticaria, most are idiopathic or post viral.
2. If urticaria occurs with swelling of the tongue or throat, difficulty breathing or low blood pressure, anaphylaxis should be suspected. Urgent administration of adrenaline and medical assessment is required. See Anaphylaxis.
3. Acute urticaria can be effectively treated with a non-sedating antihistamine.

Background

• Pruritic, elevated skin lesions surrounded by erythematous base commonly described as "hives"
• Due to transient extravasation of plasma into the dermis. It is a common condition - 25% of individuals will have it at some stage
• Deeper subcutaneous extension is much less common and termed angioedema. It involves face (eyelids, lips, tongue), hands and feet, and sometimes other areas ( trunk, genitalia, mucous membranes)
• Acute Urticaria (<6 weeks) Chronic Urticaria (>6 weeks).

Assessment

History:

• Explore events a few hours or days before onset of rash
• Information regarding the rash: the frequency, timing, duration and pattern of recurrence of lesions; the number, shape, size, site and distribution of lesions
• A specific cause is not identified in most of the cases (Idiopathic)

An allergic cause for hives should be suspected if episodes are rare, short-lived and occur under specific circumstances, for example:

• Only when exercising
• Always within 1-2 hours of a meal
• When symptoms involving other organs occur around the same time, such as stomach pain, vomiting, difficulty breathing or dizziness

Other causes are:

• Infections including viruses, bacteria and parasites
• Medications including antibiotics like penicillin, cefaclor (5-21 days after commencing course), amoxycillin, etc.
• Contact allergy to plants, animals or latex
• Foods are infrequent causes
• Bites and stings
• Physical triggers may include pressure, cold, exercise and rarely water
• Urticaria prior to menstruation (autoimmune progesterone dermatitis)
• Autoimmune conditions may present with urticaria  

Examination:

Assess for signs of anaphylaxis.

Erythematous raised skin lesion (Wheal)

• Localised or generalised
• Well circumscribed but often coalescent
• May be intensely pruritic with excoriation
• Vary in size from tiny flat papules to large raised plaques
• Flat centre with raised erythematous edge
• Diagnostic feature is polymorphic appearance and transience of individual lesion.
  

If recurrent angioedema without wheals, think of C1 esterase inhibitor deficiency .

Blotchy rash typical of urticaria

Urticarial lesions with typical clear skin in centre. These are not "target lesions"

Differential diagnosis of urticaria

Erythema multiforme

How to distinguish? EM is:

• Usually not itchy
• Does not move around - individual lesions perist for days
• Has target lesions with a central papuler, blister, purpura or ulcer.
• Often has mucosal involvement

Rare differentials

• Urticarial vasculitis (often lesions are painful and longer lasting), including HSP
• Mastocytosis
• Auriculotemporal syndrome (facial erythema in distribution of trigeminal nerve)
• Juvenile Rheumatoid Arthritis
• Serum sickness
• Pityriasis rosea (early lesions)

Management

Investigations: Usually not indicated for acute urticaria

Treatment:

Remove identifiable cause if any.

If symptomatic:

• Cool Compresses
• Avoid aggravating factors such as avoiding excessive heat or spicy foods.
• Aspirin and other NSAIDs should also be avoided as they often make symptoms worse.
• Anti-histamines to alleviate itching. A non-sedating antihistamine is preferred.

Cetirizine (Zyrtec) 0.25mg/kg/dose (adult 10mg) 12-24H oral. Can give up to 4 times the recommended dose to a maximum total daily dose of 40mg. Can be used in children from 6 months of age

• Steroid creams do not work. For severe cases, not responding to increased doses of non-sedating antihistamines, a single dose of oral prednisolone may be considered.
  

Consider consultation with local paediatric team when:

• Associated bruising or systemic features (need to exclude urticarial vasculitis or chronic urticaria as a manifestation of another disease process)
• Anaphylaxis
• Angioedema
• Age <6 months
• Chronic urticaria (>6 weeks)

Consider transfer when:

Child requiring care beyond the comfort level of the hospital.

For emergency advice and paediatric or neonatal ICU transfers, call the Paediatric Infant Perinatal Emergency Retrieval (PIPER) Service: 1300 137 650.

Consider discharge when:

Anaphylaxis is excluded.

Most patients do not need admission for urticaria.

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Last Updated January 2019