An updated version of the international guideline for urticaria covers the definition and classification of urticaria and outlines expert-guided and evidence-based diagnostic and therapeutic approaches for the different subtypes of urticaria.It explains:

Definition 

Urticaria is a condition characterized by the development of wheals (hives), angioedema or both.

Classification of urticaria based on its duration and the relevance of eliciting factors

Urticaria is classified based on its duration as acute (≤6 weeks) or chronic (>6 weeks) and also as spontaneous (no definite eliciting factor involved) or inducible (specific definite factor involved).

Chronic urticaria subtypes:

Chronic spontaneous urticaria (CSU) – Spontaneous appearance of wheals, angioedema or both for >6 weeks due to known or unknown causes.

Inducible urticaria – Symptomatic dermographism, cold urticaria, delayed pressure urticaria, solar urticaria, heat urticaria, vibratory angioedema, cholinergic urticaria, contact urticaria andaquagenicurticaria.

Differential diagnoses of urticaria:

• Maculopapular cutaneous mastocytosis (urticaria pigmentosa) and indolent systemic mastocytosis involving the skin
• Mast cell activation syndrome (MCAS)
• Urticarial vasculitis
• Bradykinin-mediated angioedema (e.g., hereditary angioedema[HAE])
• Exercise-induced anaphylaxis
• Cryopyrin-associated periodic syndromes (CAPS; urticarial rash, recurrent fever attacks, arthralgia or arthritis, eye inflammation, fatigue and headaches), that is, familial cold autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) or neonatal onset multisystem inflammatory disease (NOMID).
• Schnitzlers syndrome
• Gleichs syndrome (episodic angioedema with eosinophilia)
• Wells syndrome (granulomatous dermatitis with eosinophilia/eosinophilic cellulitis)
• Bullous pemphigoid (prebullous stage)
• Adult-onset Stills disease (AOSD).

Routine diagnostic tests (recommended) for the diagnosis of urticaria:

• Acute spontaneous urticaria- No routine diagnostic tests (recommended)
• CSU - Differential blood count, erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP), IgG anti-TPO and total IgE
• Cold urticaria- Cold provocation and threshold test
• Delayed pressure urticaria- Pressure test and threshold test
• Heat urticaria- Heat provocation and threshold test
• Solar urticaria-Ultraviolet (UV) and visible light of different wavelengths and threshold test
• Symptomatic dermographism
• Elicit dermographism and threshold test- Differential blood count, ESR or CRP
• Vibratory angioedema- Test with vibration, for example, Vortex-mixer
• Aquagenicurticaria- Provocation testing
• Cholinergic urticaria- Provocation and threshold testing
• Contact urticaria- Provocation testing.
• It is recommended that differential diagnoses be considered in all patients with signs or symptoms suggestive of chronic urticaria based on the guideline algorithm.
• It is recommended to limit investigations in CSU including basic tests like differential blood count, CRP and/or ESR, and in specialized care total IgE and IgG anti-TPO, and more biomarkers as appropriate.
• It is recommended to perform further diagnostic measures based on the patient history and examination, especially in patients with long-standing and/or uncontrolled diseases.
• It is recommended to use provocation testing to diagnose chronic inducible urticaria.
• Provocation threshold measurements and the urticaria control test (UCT) are recommended to measure disease activity and control in patients with chronic inducible urticaria, respectively.

Management of urticaria

• Aiming at complete symptom control in urticaria, considering as much as possible the safety and the quality of life of each patient is recommended.
• It is recommended to advise patients with CSU to discontinue a medication that is suspected to worsen the disease, like nonsteroidal anti-inflammatory drugs (NSAIDs).
• Second-generation H1-antihistamine is recommended as a first-line treatment for all types of urticaria.
• Second-generation H1-antihistamine can be up dosed up to fourfold in patients with chronic urticaria (CU) unresponsive to a standard-dosed second-generation H1-antihistamines as a second-line treatment before considering other treatments.
• Second-generation H1-antihistamines should be taken regularly for the treatment of patients with CU.
• It is recommended to add omalizumab for the treatment of patients with CU unresponsive to high-dose second-generation H1-antihistamines.
• Ciclosporin can be used for treating the patients with CU unresponsive to a high dose of second-generation H1-antihistamine and omalizumab.
• Recommendation is against the long-term use of systemic glucocorticosteroids in CU.
• A short course of rescue systemic glucocorticosteroids in patients with an acute exacerbation of CU can be considered.
• The same treatment algorithm with caution (e.g., weight-adjusted dosage) can be used in children with CU.
• The same treatment algorithm can be used with caution both in pregnant and lactating women after a risk-benefit assessment. Drugs contraindicated or not suitable for pregnancy should not be used.

Source: Zuberbier T, Latiff AH, Abuzakouk M, et al. The internationalEAACI/GA²LEN/EuroGuiDerm/APAAACI guideline for the definition, classification, diagnosis, and management of urticaria. Allergy. 2022;77(3):734-66.