Hives — medically known as urticaria — are one of the most common reasons parents bring their child to see an allergy specialist. The sudden appearance of raised, itchy, blotchy welts on the skin can be alarming, particularly when they appear without an obvious cause. This article explains what causes hives in children, the difference between acute and chronic urticaria, and when specialist assessment is needed.

What Are Hives?

Hives are raised, itchy welts on the skin that can appear anywhere on the body. They are typically red or skin-coloured, vary in size from a few millimetres to several centimetres, and may join together to form larger patches. Individual hives usually resolve within 24 hours, but new ones may continue to appear.

Hives are caused by the release of histamine and other chemicals from mast cells in the skin. This causes fluid to leak from small blood vessels, producing the characteristic raised weal.

Acute Urticaria

Acute urticaria is defined as hives lasting less than 6 weeks. It is very common in children and is usually caused by:

  • Viral infections: The most common cause of acute urticaria in children — many viral illnesses trigger a brief episode of hives
  • Food allergy: Particularly peanut, tree nuts, egg, cow's milk, fish and shellfish
  • Insect stings: Bee or wasp venom
  • Medications: Antibiotics (particularly penicillin), NSAIDs (ibuprofen)
  • Contact allergens: Latex, plants, cosmetics

Acute urticaria caused by viral infection usually resolves spontaneously within a few days to weeks. Antihistamines help control symptoms in the meantime.

Chronic Urticaria

Chronic urticaria is defined as hives occurring on most days for more than 6 weeks. It is less common in children than adults but does occur. In most cases of chronic urticaria, no external trigger is identified — this is called chronic spontaneous urticaria (CSU). It is caused by the immune system spontaneously activating mast cells, not by allergy.

Chronic urticaria can be very distressing for children and families. It requires specialist assessment and ongoing management. Allergy testing is usually not helpful in chronic spontaneous urticaria, as it is not caused by IgE-mediated allergy.

Physical Urticaria

Some children develop hives in response to physical stimuli:

  • Dermographism: Hives that appear when the skin is scratched or rubbed
  • Cold urticaria: Hives triggered by cold temperatures or cold water
  • Cholinergic urticaria: Hives triggered by heat, exercise or emotional stress
  • Pressure urticaria: Hives at sites of sustained pressure (e.g. waistband, bra strap)
  • Solar urticaria: Hives triggered by sunlight

Treatment of Urticaria in Children

Antihistamines

Non-sedating antihistamines (cetirizine, loratadine) are the first-line treatment for urticaria in children. They block the action of histamine and reduce itching and weal formation. For chronic urticaria, regular daily antihistamines are more effective than taking them only when hives appear. Higher-than-standard doses are often needed for adequate control.

Omalizumab

For children aged 12 and over with chronic spontaneous urticaria that does not respond adequately to antihistamines, omalizumab (Xolair) is a licensed treatment. It is a biologic medication given by injection every 4 weeks. Dr Anandarajan can advise on eligibility and arrange referral for omalizumab if appropriate.

When Should I Seek Specialist Assessment?

Seek specialist assessment at Belfast Children's Allergy Clinic if:

  • Your child has had hives on most days for more than 6 weeks (chronic urticaria)
  • Hives are accompanied by swelling of the lips, tongue or throat (angioedema)
  • You suspect a food or drug allergy is causing the hives
  • Hives are not controlled by over-the-counter antihistamines
  • Your child has had hives with breathing difficulties or collapse (seek emergency care immediately)

Book an Appointment

Call 028 9066 7878 or book online at kph.fyi/Book-MAnandarajan. No GP referral is required.