[Round Table: Urticaria and angioedema: introduction and classification].

Urticaria and angioedema are common diseases in children and adults. Approximately 15-25% of the population will have urticaria or angioedema at least once in their life-time. Urticaria is characterized as the appearance of erythematous, circumscribed, elevated, pruritic, edematous swelling of the upper dermal tissue. Erythematous swelling of the deeper cutaneous and subcutaneous tissue is called angioedema. In angioedema lesions are less pruritic but pain and burning are common. Urticaria may occur in any part of the body, whereas angioedema often involves face, extremities or genitalia. In contrast to other forms of edema there are not symmetric distribution. Urticaria and angioedema are often associated. Urticaria is considered acute if symptoms are present for less than 6 weeks, but usually in childhood lesions disappear in a few days. In chronic urticaria symptoms are longer than 6 weeks; if the episodes were of shorter duration than the symptoms-free periods urticaria is considered recurrent. Acute urticaria has been reported to be the common type in childhood and chronic urticaria is more frequent in adults. Acute urticaria is usually a self-limited benign disease in young children. Nevertheless it is an uncomfortable nuisance, interfering daily activities and sleep, and produces psychosocial impact in patients and parents (an altered self-image is always an alarming situation). Urticaria is a frequent cause of emergency room visit but few patients need to be admitted. Urticaria has long been believed to be an allergic disease but clinically it has rare been proved to be so. The basic mechanism involves the release of diverse vasoactive mediators that arise from the activation of cells or enzymatic pathways. Histamine is the best known of these substances, and elicits the classic triple response consisting of vasodilatation (erythema), increased vascular permeability (edema) and an axon reflex that increases reaction. In contrast to simple symptoms and easy diagnosis of urticaria, etiologic factors are often difficult to establish. Urticaria can be classified according to the eliciting factors and the different pathomechanisms. According to several works, clinical history carried out by a trained physician can be regarded as the most valuable diagnostic tool and extensive screening test do not contribute to etiologic diagnosis of urticaria. Only a few specific tests appeared to be valuable at this respect. In different studies about children urticaria, the most common etiological factors have been identified as infection, physical urticaria, food allergy, drug adverse reaction, parasitic infestation and papular urticaria. The aim of this work-shop is to define, describe and discuss these frequent problems.