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
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Last Updated January 2019