From the Guidelines

Urticaria (hives) in children is a common skin condition characterized by itchy, raised welts that can be acute, episodic, or chronic.

Ordinary urticaria: can be acute (up to 6 weeks of continuous activity) or chronic (6 weeks or more of continuous activity) 1
Physical urticarias: triggered by physical stimuli such as mechanical, thermal, or vibratory stimuli 1
Contact urticaria: occurs when an allergen is absorbed through the skin or mucous membranes 1
Urticarial vasculitis: a systemic disease characterized by inflammation of small blood vessels and urticaria-like lesions 1
Autoinflammatory syndromes: a group of disorders that present with urticaria, fever, and other systemic symptoms 1

Weal duration: can help distinguish between different types of urticaria, with ordinary urticaria lasting 2-24 hours and physical urticaria lasting less than 1 hour 1
Associated symptoms: may include angioedema, fever, and malaise 1

Acute or episodic ordinary urticaria: no investigations are required except where suggested by the history, and skin-prick testing or CAP fluoroimmunoassay may be used to confirm IgE-mediated reactions 1
Chronic urticaria: may require consultation with an allergist-immunologist to identify underlying causes and develop a treatment plan 1

From the Research

Urticaria is a common disease that can affect individuals of all age groups, characterized by lesions known as hives or wheals, which can appear anywhere on the body 2.
It is classified into acute and chronic forms, with the latter referring to a condition that lasts for more than 6 weeks 3, 4, 5.
Acute urticaria is often due to viral infections, while chronic urticaria can be caused by various factors, including physical factors, infections, foods, additives, aeroallergens, and drugs 3, 4, 6.

Infections are a common cause of urticaria in children, with urinary tract infections, Chlamydia pneumoniae, and Helicobacter pylori being frequently documented 6.
Other triggers include foods, drugs, insect stings, contrast media, vaccination, latex, and medical diseases 3, 4.
Physical factors, such as cold or heat, can also trigger urticaria in children 4, 6.

The diagnosis of urticaria is based on patient history and physical examination, with laboratory tests and confirmatory allergy tests individualized and guided by history 3, 4.
Treatment includes identification and removal of the triggering agent, reduction of non-specific factors that may contribute to the urticaria, and use of anti-H1 antihistamines 4, 5.
In cases of chronic urticaria, second-generation H1 antihistamines are the first line of treatment, with other therapies considered in unresponsive patients 5.

Chronic spontaneous urticaria (CSU) is the most common type of chronic urticaria in children 3.
Chronic inducible urticaria (CindU) is less common but important to diagnose and manage appropriately to reduce the risk of severe reactions 3.
Other types of urticaria, such as urticarial vasculitis and mast cell disorders, should also be considered in the differential diagnosis of pediatric urticaria 2.