This evidence- and consensus-based guideline was developed following the methods recommended by Cochrane and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group. The conference was held on 1 December 2016. It is a joint initiative of the Dermatology Section of the European Academy of Allergology and Clinical Immunology (EAACI), the EU-founded network of excellence, the Global Allergy and Asthma European Network (GA²LEN), the European Dermatology Forum (EDF) and the World Allergy Organization (WAO) with the participation of 48 delegates of 42 national and international societies. This guideline was acknowledged and accepted by the European Union of Medical Specialists (UEMS). Urticaria is a frequent, mast cell-driven disease, presenting with wheals, angioedema, or both. The lifetime prevalence for acute urticaria is approximately 20%. Chronic spontaneous urticaria and other chronic forms of urticaria are disabling, impair quality of life and affect performance at work and school. This guideline covers the definition and classification of urticaria, taking into account the recent progress in identifying its causes, eliciting factors and pathomechanisms. In addition, it outlines evidence-based diagnostic and therapeutic approaches for the different subtypes of urticaria.

This guideline is the result of a systematic literature review using the 'Grading of Recommendations Assessment, Development and Evaluation' (GRADE) methodology and a structured consensus conference held on 28 and 29 November 2012, in Berlin. It is a joint initiative of the Dermatology Section of the European Academy of Allergy and Clinical Immunology (EAACI), the EU-funded network of excellence, the Global Allergy and Asthma European Network (GA(2) LEN), the European Dermatology Forum (EDF), and the World Allergy Organization (WAO) with the participation of delegates of 21 national and international societies. Urticaria is a frequent, mast cell-driven disease, presenting with wheals, angioedema, or both. The life-time prevalence for acute urticaria is approximately 20%. Chronic spontaneous urticaria and other chronic forms of urticaria do not only cause a decrease in quality of life, but also affect performance at work and school and, as such, are members of the group of severe allergic diseases. This guideline covers the definition and classification of urticaria, taking into account the recent progress in identifying its causes, eliciting factors and pathomechanisms. In addition, it outlines evidence-based diagnostic and therapeutic approaches for the different subtypes of urticaria. This guideline was acknowledged and accepted by the European Union of Medical Specialists (UEMS).

This guideline, together with its sister guideline on the classification of urticaria (Zuberbier T, Asero R, Bindslev-Jensen C, Canonica GW, Church MK, Giménez-Arnau AM et al. EAACI/GA(2)LEN/EDF/WAO Guideline: definition, classification and diagnosis of urticaria. Allergy 2009;64: 1417-1426), is the result of a consensus reached during a panel discussion at the Third International Consensus Meeting on Urticaria, Urticaria 2008, a joint initiative of the Dermatology Section of the European Academy of Allergology and Clinical Immunology (EAACI), the EU-funded network of excellence, the Global Allergy and Asthma European Network (GA(2)LEN), the European Dermatology Forum (EDF) and the World Allergy Organization (WAO). As members of the panel, the authors had prepared their suggestions regarding management of urticaria before the meeting. The draft of the guideline took into account all available evidence in the literature (including Medline and Embase searches and hand searches of abstracts at international allergy congresses in 2004-2008) and was based on the existing consensus reports of the first and the second symposia in 2000 and 2004. These suggestions were then discussed in detail among the panel members and with the over 200 international specialists of the meeting to achieve a consensus using a simple voting system where appropriate. Urticaria has a profound impact on the quality of life and effective treatment is, therefore, required. The recommended first line treatment is new generation, nonsedating H(1)-antihistamines. If standard dosing is not effective, increasing the dosage up to four-fold is recommended. For patients who do not respond to a four-fold increase in dosage of nonsedating H(1)-antihistamines, it is recommended that second-line therapies should be added to the antihistamine treatment. In the choice of second-line treatment, both their costs and risk/benefit profiles are most important to consider. Corticosteroids are not recommended for long-term treatment due to their unavoidable severe adverse effects. This guideline was acknowledged and accepted by the European Union of Medical Specialists (UEMS).

Summary Background The infection caused by the recently identified SARS‐CoV‐2, called coronavirus disease‐19 (COVID‐19), has rapidly spread throughout the world. With the exponential increase of patients worldwide, the clinical spectrum of COVID‐19 is being better defined and new symptoms are emerging. Numerous reports are documenting the occurrence of different cutaneous manifestations in patients with COVID‐19. Objectives To provide a brief overview of cutaneous lesions associated with COVID‐19. Methods A literature search was performed in the PubMed, Scopus and Web of Science databases up to 30 April 2020. This narrative review summarizes the available data regarding the clinical and histological features of COVID‐19‐associated skin manifestations. Results The literature reports showed a great heterogeneity in COVID‐19‐associated cutaneous manifestations, as well as in their latency periods and associated extracutaneous symptoms. Pathogenic mechanisms are unknown, although the roles of a hyperactive immune response, complement activation and microvascular injury have been hypothesized. Based on our experience and the literature data, we subdivided the reported cutaneous lesions into six main clinical patterns: (i) urticarial rash; (ii) confluent erythematous–maculopapular–morbilliform rash; (iii) papulovesicular exanthem; (iv) chilblain‐like acral pattern; (v) livedo reticularis–livedo racemosa‐like pattern; and (vi) purpuric ‘vasculitic’ pattern. These six patterns can be merged into two main groups: the first – inflammatory and exanthematous – includes the first three groups listed above, and the second includes the vasculopathic and vasculitic lesions of the last three groups. Conclusions The possible presence of cutaneous findings leading to suspect COVID‐19 puts dermatologists in a relevant position. Further studies are needed to delineate the diagnostic and prognostic values of such cutaneous manifestations.

Our findings on CSU prevalence are consistent with those obtained in previous studies. Furthermore, this large population-based study provides important information regarding the association of CSU with demographic and clinical determinants, which have been examined in the primary-care setting.