Urticaria – the sudden appearance of itchy, raised welts that migrate across the skin, disappear, and reappear elsewhere – is alarming the first time a parent sees it. The classic picture: a child comes home from school looking normal and within an hour is covered in red welts that are moving around, and the parent who does not know what urticaria is assumes an emergency.
Understanding what urticaria is, what usually causes it in children (viral illness, overwhelmingly more often than food allergy), and what distinguishes it from the genuinely dangerous allergic response of anaphylaxis reduces both the anxiety and the inappropriate responses (unnecessary food avoidance, unneeded EpiPen prescriptions, avoidable emergency department visits).
Healthbooq (healthbooq.com) covers allergy and skin conditions in children.
What Urticaria Is
Urticaria is a skin reaction caused by histamine and other mediators released by mast cells in the dermis. The characteristic features are: wheals (raised, pale at the centre, surrounded by a red flare); itching or burning; that individual lesions resolve within 24 hours but new ones continue to appear; and that the rash migrates (appears in one area, then elsewhere).
Angioedema (deep swelling of the skin, often in the lips, eyelids, and face) can accompany urticaria. Angioedema without urticaria, or angioedema associated with pain rather than itching, can indicate a different condition (hereditary angioedema) and warrants specialist assessment.
What Causes Urticaria in Children
Viral infections are the most common cause of acute urticaria in children, accounting for up to 60-80% of acute urticaria episodes in the paediatric age group. A child who develops hives during or shortly after a respiratory or gastrointestinal illness almost certainly has viral urticaria rather than a food allergy.
This is important because parents (and sometimes healthcare providers) often assume that any urticaria, particularly following eating, represents a food allergy. In fact, in children who have eaten recently (which is most of the time), the temporal coincidence of eating and urticaria is common but the causal link is often absent. True food-triggered urticaria is usually accompanied by other features (lip tingling, mouth itch, vomiting, or anaphylaxis features) and occurs consistently with the same food on repeated exposure.
Food allergy does cause urticaria, but it is a much less common cause in children than viral illness. The Foods most commonly implicated in food-allergic urticaria are the major childhood allergens: peanuts, tree nuts, milk, egg, fish, sesame.
Physical urticarias: urticaria triggered by physical stimuli including cold, pressure, heat, exercise, or water. Cold urticaria (wheals appearing minutes after cold exposure) is a treatable condition managed with antihistamines and is important to diagnose because cold water immersion can cause systemic reactions.
Chronic spontaneous urticaria (CSU): urticaria persisting for more than 6 weeks without a specific identifiable trigger, occurring daily or almost daily. In children, this is rarely caused by allergy or a specific trigger. It is an autoimmune condition in many cases, associated with anti-FcεRI or anti-IgE autoantibodies. Treatment involves daily non-sedating antihistamines, with omalizumab (anti-IgE monoclonal antibody) for refractory cases.
Treatment
Non-sedating antihistamines are first-line for acute urticaria: cetirizine and loratadine are the most widely used in children. They do not stop the underlying mast cell activation but prevent histamine from binding to H1 receptors and reduce itch and wheal formation. For acute urticaria, antihistamines are given until the episode resolves.
Sedating antihistamines (chlorphenamine) are less appropriate for routine use because the sedation adds little therapeutic benefit and impairs function; they are sometimes used at night when itch is preventing sleep.
Steroids (prednisolone) are used for severe or extensive acute urticaria where antihistamines are insufficient, particularly if the child is significantly distressed or there is swelling.
When Urticaria Is Part of Anaphylaxis
Urticaria without anaphylaxis features is not an emergency and does not require adrenaline. The difference: anaphylaxis involves at least two body systems, with life-threatening airway, breathing, or circulation involvement. A child with hives only, who is well, alert, and breathing normally, needs antihistamines, not an EpiPen.
A child with hives AND throat tightness, difficulty breathing, wheeze, pallor, or collapse has anaphylaxis – use the EpiPen and call 999.
Key Takeaways
Urticaria (hives) is one of the most common allergic skin reactions in children, characterised by itchy wheals (raised red or skin-coloured bumps surrounded by a flare) that can appear anywhere on the body, are transient (individual wheals lasting less than 24 hours), and are often migratory (appearing in one place and then another). Acute urticaria (lasting less than 6 weeks) is most commonly triggered by viral infections in children rather than food allergy, which surprises many parents. Chronic urticaria (lasting more than 6 weeks) is rarely caused by allergy in children and is usually spontaneous (chronic spontaneous urticaria). Non-sedating antihistamines (cetirizine, loratadine) are first-line treatment. Urticaria without anaphylaxis features does not require adrenaline.
