Urticaria and Angioedema in Children

Prepared and reviewed by the PrepElephant Academic Review Team

First published 14 Oct 2026 · Spot an error?

Reference basis: Nelson Textbook of Pediatrics; Ghai Essential Pediatrics

On this page

Direct answer
What you must remember
Separating urticaria from hereditary angioedema
Where the exam tests these conditions
Frequently asked questions
Related topics

Direct answer

Urticaria is an eruption of itchy wheals, and angioedema is deeper swelling of the dermis and subcutis. In children, acute urticaria lasts under six weeks and is most often triggered by infections, foods or drugs, while chronic urticaria persists beyond six weeks. Hereditary angioedema, caused by C1 esterase inhibitor deficiency, produces non-itchy swelling without wheals and does not respond to antihistamines.

What you must remember

Acute versus chronic: acute urticaria lasts under six weeks, and chronic urticaria persists beyond six weeks, often without an identifiable trigger.
Wheal features: itchy, raised lesions that blanch under pressure, with individual wheals settling within 24 hours.
Angioedema: deeper swelling of the lips, eyes, hands or genitals, which may be painful rather than itchy, and visceral swelling can cause abdominal pain.
Hereditary angioedema: C1 esterase inhibitor deficiency, usually autosomal dominant, with low C4 between attacks and no response to antihistamines or steroids.
Acute treatment: a non-sedating second-generation antihistamine for urticaria, and intramuscular adrenaline when there is anaphylaxis or airway involvement.
Chronic urticaria: second-generation antihistamines first, with omalizumab reserved for refractory disease in older children and adolescents.
HAE treatment: C1 esterase inhibitor concentrate, icatibant or lanadelumab for attacks and prophylaxis, with androgens such as danazol generally avoided in children.
Drugs to avoid in HAE: ACE inhibitors and oestrogen-containing contraceptives can trigger attacks.

Separating urticaria from hereditary angioedema

The mediator decides the treatment, so the mediator is identified before choosing a drug. Histamine drives urticaria, while bradykinin drives hereditary angioedema, and this single difference explains most of the treatment contrast.

Feature	Urticaria	Hereditary angioedema
Skin lesion	Itchy wheals	Non-itchy swelling, no wheals
Main mediator	Histamine	Bradykinin
Antihistamine response	Usually good	Poor
Key test	Clinical history and exam	Low C4, low C1 esterase inhibitor level or function
Family history	Uncommon	Often present

Recurrent swelling without wheals should prompt a C4 and C1 inhibitor check rather than a steroid trial, especially when the swelling does not fit the usual allergic pattern. Chronic urticaria usually needs no extensive allergy testing, because guidelines generally advise a targeted history and limited investigations, such as a complete blood count when systemic features are present.

Patients with angioedema of the airway or gut need urgent assessment, since laryngeal swelling can progress quickly and threaten the airway.

Where the exam tests these conditions

Questions focus on the mediator, the drugs to avoid and the blood test that points to hereditary angioedema. These traps are common.

Trap: treating recurrent swelling without wheals as allergic urticaria and giving steroids. Correct: non-itchy swelling without wheals suggests bradykinin-mediated angioedema, which needs C4 and C1 inhibitor assessment.
Trap: giving an ACE inhibitor to a child with hereditary angioedema. Correct: ACE inhibitors raise bradykinin levels and can trigger attacks, so they must be avoided.
Trap: ordering extensive allergy panels for chronic urticaria by default. Correct: routine panels rarely identify a cause, so a targeted history and limited tests are preferred.

Frequently asked questions

What is the difference between acute and chronic urticaria?

Acute urticaria lasts less than six weeks and is often triggered by infection, drugs or foods. Chronic urticaria persists beyond six weeks and frequently has no identifiable trigger.

Does an antihistamine work in hereditary angioedema?

Antihistamines do not work well in hereditary angioedema, because the swelling is driven by bradykinin rather than histamine. C1 esterase inhibitor concentrate, icatibant or lanadelumab are used instead for attacks or prophylaxis.

Which blood test points to hereditary angioedema?

Low serum C4 with a low C1 esterase inhibitor level or function points to hereditary angioedema. C4 is consumed because C1 inhibitor is absent, so this pattern is especially useful in a child with recurrent swelling and a family history.

Why should ACE inhibitors be avoided in hereditary angioedema?

ACE inhibitors reduce breakdown of bradykinin, so they can precipitate attacks of angioedema in patients with hereditary angioedema. Oestrogen-containing contraceptives can also trigger attacks in susceptible patients.