Urticaria

In childhood, the prevalence of urticaria is 15-20%. The incidence is 5% in the early years of life and it is less common in the first months of life. Urticaria is caused by mast cell degranulation. Mast cells may be activated by an immunological or non-immunological mechanism. Released mediators cause pruritus and oedema.

Signs and symptoms

It is characterised by the appearance of wheals, circumscribed elevations on the skin, pinkish-red in colour, with a normal skin surface. The shape and size are variable. The characteristic feature of wheals is that they are evanescent, i.e. they last from a few minutes to a few hours and do not exceed 24 hours, subsequently disappearing from their original location and reappearing in other locations. The form varies depending on the location; in fact where the tissue is looser, like on the eyelids or lips, it looks like angioneurotic oedema and it is called angioedema. It may also affect the mucous membranes, lasts longer for up to 72 hours, and may be accompanied by pain or discomfort.

Urticaria is most often diffuse. The wheals may vary in appearance depending on the morphology, annular, circinate. They are sometimes large and the condition is then called giant urticaria. The course is towards regression, usually without sequelae, but they tend to recur. Urticaria with purpura comprises a haemorrhagic element which leaves pigmentary sequelae (urticaria pigmentosa).

In the first years of life urticaria presents with wheals and angioedema; in older children it is characterised only by wheals. Pruritus is the main symptom. Depending on the duration, distinction is made between an acute form which lasts less than 6 weeks and a chronic form which lasts over 6 weeks.

There is also chronic intermittent or recurrent urticaria with episodes of urticaria alternating with periods of remission that may even last a few weeks. Small children of under 3 years of age present a particular form of acute urticaria defined as multiform or annular. This variety, which often comes after episodes of drug-induced infection, is characterised by polycyclic lesions with central resolution and/or purplish-brown sequelae, present in variable number; transient oedema of the extremities is associated. Pruritus is usually absent and often the symptoms are characterised by joint pain and functional impotence.

Chronic urticaria is classified in two varieties: a spontaneous form, in which no triggering factors are associated, and an inducible form with known triggering factors; the latter includes physical urticaria, for example pressure urticaria. Sometimes the two forms are present simultaneously. Food-induced urticaria is highly exceptional. However, during urticaria flare-ups, it is good practice to reduce intake of histamine-rich foods.

The allergic mechanism is prevalent in atopic subjects.

Urticaria and atopy

In both the acute form and the chronic form, in children the link with atopy is high. Infantile urticaria is 2-5 times more common in atopic subjects; this association is more marked than in adults. Recurrent acute urticaria is 10 times more common in atopic subjects.

Treatment

Antihistamines are the drugs of first choice and they are used for 2-3 weeks; drugs authorised for the age are recommended. Non-steroidal anti-inflammatories (e.g. ibuprofen) and histamine-rich foods should be avoided. Steroids should only be administered in the most severe forms and for only a few days.

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