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See also

Anaphylaxis
C1 esterase inhibitor deficiency
IgE-mediated food allergy
Serum Sickness and Serum Sickness like reactions

Key Points

1. There are many causes for urticaria, most are idiopathic or viral 
2. If urticaria occurs with involvement of other systems (eg airway, respiratory, cardiovascular, gastrointestinal), 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

• Urticaria is a common skin condition characterised by recurrent, transient, raised pruritic lesions (wheals), more commonly known as “hives”
• Occurs due to transient extravasation of plasma into the superficial dermis, as a consequence of mast cell degranulation and histamine release
• Less commonly, localised deeper subcutaneous swelling (angioedema) may co-exist or may occur independently
• Acute urticaria lasts for less than 6 weeks and chronic urticaria occurs most days for more than 6 weeks

• A specific cause is not identified in many cases of urticaria (idiopathic)
• Urticaria is rarely due to serious underlying disease
• Infection
  • Viral infection is a common cause of urticaria in children
  • Urticaria may occur both during and after an illness when the child is otherwise well
• Allergy
  • Reactions to food, medication or insect stings can appear as urticaria
  • Suspect if episodes are rare, short-lived and occur under specific circumstances:
    • Only when exercising
    • Always within 1-2 hours of a meal
    • When other symptoms occur around the same time such as abdominal pain, vomiting, breathing difficulty or dizziness
  • Urticaria usually appears within 1-2 hours of the exposure and disappears within 6-8 hours
    • Urticaria lasting days are almost never due to allergy (with the exception of some medication allergies)
  • Urticaria occurring at the time of antibiotic use is often due to the underlying infection rather than an allergy to the antibiotic. Take a detailed  drug allergy history and consider specialist drug allergy clinic referral
• Other causes  
  • Contact and irritant dermatitis (eg to plants, animals or latex)
  • Physical triggers (pressure, heat, cold, exercise and rarely water)
  • Urticaria prior to menstruation (autoimmune progesterone dermatitis)
  • Systemic diseases (eg autoimmune, connective tissues and lymphoproliferative disorders)  
  • Stress is very rarely the cause, but may make the symptoms worse
• Chronic urticaria (>6 weeks) is usually idiopathic, but can also be inducible (associated with a physical trigger) or autoimmune-related
• Angioedema is often idiopathic. Similar to urticaria, viral infections are a common cause in the paediatric population. Other causes include allergen triggers such as medications (NSAIDs, ACE inhibitors, antibiotics), foods and insect stings

Assessment

History

• Events preceding (hours to days) onset of rash
• Number, shape, size, site and distribution of lesions
• Frequency, timing, duration and pattern of recurrence of lesions
• Urticarial lesions often come and go over several hours, but can be days or weeks
• Pruritis
• Possible causes/triggers (see above)
• Systemic features (eg associated with autoimmune conditions)

Examination

• Rapidly assess for signs of anaphylaxis
• Elevated skin lesions with a flat pale centre, surrounded by an erythematous base (wheals)
• Localised or generalised, any part of the body
• Vary in size (millimetres to centimetres)
• Well circumscribed but often coalescent
• May appear within minutes and usually resolve within 24 hours
• Transient and appear to “migrate”, disappearing within minutes to hours from one location and reappearing elsewhere
• In an area where a wheal has faded, there may be residual purple discolouration
• Polymorphic and transient – diagnostic features
• Excoriation (due to intense pruritis)
• Signs of underlying cause (eg infection, systemic disease)
• Angioedema
• Swelling which frequently affects the face and lips, but can also affect the hands, feet, trunk and genitalia
• Compared to wheals, the swollen lesions are larger, may be painful or uncomfortable rather than pruritic, and may last longer taking up to 72 hours to resolve
  
  

Blotchy rash typical of urticaria

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Rare differential diagnoses

• Urticarial vasculitis (including HSP): lesions are usually painful rather than pruritic, last >48 hours and leave discolouration on the skin
• Serum sickness and serum sickness-like reactions
• Mastocytosis
• Auriculotemporal syndrome (facial erythema in distribution of trigeminal nerve)
• Juvenile rheumatoid arthritis
• Pityriasis rosea (early lesions)

Urticaria is not a feature of C1 esterase inhibitor deficiency. If recurrent angioedema without wheals, think of C1 esterase inhibitor deficiency

Management

Investigations

• Almost never indicated for acute urticaria
  • Routine allergy tests are generally not required. This is a common misconception and may require discussion with the family
• May be indicated for chronic urticaria if there are features suggestive of an underlying cause

Treatment

Acute urticaria

• Most cases only last for a few days or weeks and resolve without any treatment
• Remove identifiable triggers
• Avoid aggravating factors (eg excessive heat or spicy foods)
• Avoid NSAIDs as they often make symptoms worse
• Cool compress
• Antihistamines to alleviate itching
  • Non-sedating formulation is preferred 
  • Eg cetirizine
    • 6-11 months: 0.25 mg/kg (max 2.5 mg) oral daily
    • 1-2 years: 2.5 mg oral twice daily
    • 2-6 years: 5 mg oral daily or 2.5 mg oral twice daily
    • 6-12 years: 10 mg oral daily or 5 mg oral twice daily
    • 12-18 years: 10 mg oral daily
• A single dose of oral prednisolone 0.5-1 mg/kg (max 60 mg) may be considered in severe cases not responding to antihistamines
• Steroid creams are not effective
  
  

Chronic urticaria

• Initial treatment is the same as for acute urticaria
• If ongoing symptoms
• Cetirizine dose can be increased up to 4 times the recommended daily dose. Eg in children 6 years and older, cetirizine maximum total daily dose of 40mg
• A sedating antihistamine may be added
• If symptoms persist, seek specialist advice. Immunomodulator therapy may be considered in consultation with allergy specialist

Consider consultation with local paediatric team when

• Associated fever, bruising, joint pain or other 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, see Retrieval Services

Consider discharge when

• Anaphylaxis has been excluded
• Most patients do not need admission for urticaria

Parent information

Last updated March 2023