See also
Anaphylaxis
Key points
- There are many causes for
urticaria, most are idiopathic or post viral
- 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
- 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
Parent
information sheet
Parent Information Sheet (HTML version)
Last Updated January 2019