Urticaria not associated with anaphylaxis: management in children

Urticaria can be defined as either acute, lasting less than 6 weeks in duration, or chronic, either lasting longer than 6 weeks or with regular recurrent episodes. Chronic urticaria may be associated with physical stimuli (e.g. dermographism, cold, heat, pressure) and often has an autoimmune component. A detailed history to attempt to identify a trigger, the duration of symptoms, the presence of any facial or mouth swelling, wheezing or difficulty breathing is important. 

Triggers for urticaria can include viral illnesses, different allergens and drugs (e.g. penicillin and NSAIDS).  In many cases, the trigger is unclear. 

Urticaria due to IgE mediated allergy typically occurs within minutes of exposure to the allergen (maximum 1-2 hours) and lasts for a short period (minutes to a few hours). 

Urticaria due to viral illness or a drug reaction can last for several hours, days or sometimes weeks. The typical history for urticaria secondary to a viral illness is one where the child has had viral symptoms for a few days prior to the development of an urticarial rash. However, it can appear “out of the blue” with no obvious prodrome. 

The rash may come and go over several days, and may not appear to respond to antihistamines. If children wake up at night or first thing in the morning with a widespread urticarial rash, the mechanism is very unlikely to be allergy. 

Further investigations are not usually required in the ED, unless there is evidence of systemic disease or additional symptoms such as bruising, which could suggest urticarial vasculitis. If this is suspected, the following investigations should be done in the ED - FBC, ANA, C3 and C4 and TFT - these patients should be referred to dermatology.

• If a specific allergen is suspected, the child should be given chlorphenamine and assessed to ensure they are not developing an anaphylactic reaction. Subsequent avoidance of the potential allergen should be advised. An allergy management plan and chlorphenamine should be given at discharge and the child referred to an allergy clinic. If the history and presentation is diagnostic of a food allergy, then refer to a dietician.
• If no specific trigger is identified, management consists of an antihistamine. If the child is younger than 6 months chlorphenamine should be given. If the child is older than 6 months, a longer acting antihistamine should be used (first line long acting antihistamine is cetirizine). 

When to Refer to Dermatology Clinic

Patients should be referred if urticaria persists for longer than 3 months and is unresponsive to 3 successive trials of a long acting antihistamine, each trialled for 4-6 weeks. Children with additional symptoms such as bruising or joint swelling should also be referred to dermatology, as these symptoms may be suggestive of systemic disease. The ED discharge summary can be used to advise the GP on the criteria for referral to a Dermatology Clinic.

Cetirizine Dosage 

Chlorphenamine Dosage