Pseudoallergic reactions in chronic urticaria are associated with altered gastroduodenal permeability

EAACI/GA2LEN/EDF guideline: definition, classification and diagnosis of urticaria

This guideline is the result of a consensus reached during a panel discussion at the 2nd International Consensus Meeting on Urticaria, Urticaria 2004, a joint initiative of the European Academy of Allergology and Clinical Immunology Dermatology Section and the European Union (EU)-funded network of excellence, GA2LEN. It covers the definition and classification of urticaria, taking into account the recent progress in identifying causes, eliciting factors and pathomechanisms of this disease. We have outlined useful diagnostic approaches for different subtypes of urticaria. This guideline was, in addition, accepted by the European Dermatology Forum (EDF) and was formally approved by the European Union of Medical Specialists (UEMS).

Aktuelle Positionsbestimmung zur Bedeutung von Nahrungsmittelallergien und -unverträglichkeiten bei der Urtikaria

Foods are usually the first suspect as the cause of urticaria. However, a causal relationship is found only in special subtypes of urticaria. IgE-mediated food allergy should be clearly separated from non-allergic hypersensitivity (pseudoallergic reactions). The former may play a role in acute urticaria, particularly in patients with atopic dermatitis. The responsible food proteins vary with age. IgE-mediated sensitization can apply to food-dependent exercise-induced urticaria/anaphylaxis but more often the combination of food intake (irrespective of which type) plus exercise results in symptoms. In chronic urticaria, IgE-mediated sensitization to food is normally irrelevant while pseudoallergic reactions to food additives and perhaps also to biogenic amines may be involved. Another urticaria subtype that may be caused by food is contact urticaria which is mostly found in the context of occupational food handling. Very rarely anisakiasis and nickel may cause food-induced urticaria. Aspirin is able not only to exacerbate and aggravate urticaria but can also enhance food-dependent urticaria.

Urticaria: selected highlights and recent advances

Urticaria has been called a vexing problem and remains so today. The most important part of the diagnostic evaluation remains a comprehensive and detailed history and physical examination, supplemented with limited laboratory testing. Although acute urticaria has been relatively well understood for some time, significant and important recent advances in under-standing the pathogenesis of chronic urticaria are beginning to provide insight in this challenging field, notably the identification of many of these patients with an autoimmune etiology. Antihistamines of various types continue to represent the keystone of symptomatic treatment, with adjunctive support from medications of other classes, such as antileukotrienes, adrenergics, and immunosuppressive and anti-inflammatory agents (including steroids and cyclosporine). Although some progress has been made at improving symptomatic control of urticaria, further research and discovery are necessary before there can yet be an effective impact on the underlying course and natural history of this condition.

Chronic urticaria is associated with mast cell infiltration in the gastroduodenal mucosa

Chronic urticaria (CU) is characterized by recurrent itching skin eruptions caused by mast cell degranulation. Relapses can be provoked by food intake. The aim of this study was to investigate if the mast cell number in the gastroduodenal mucosa is increased in CU patients, and whether mast cell counting by pathologists is clinically useful. We defined two study groups: 50 disease controls (16 Belgians and 34 Italians) and 43 Belgian CU patients. Mast cells were detected using immunohistochemistry for tryptase and CD117. The mast cell number in the disease controls was 20.2/high-power filed (HPF; 133.3/mm2) in the stomach and 32.5/HPF (209.2/mm2) in the duodenum. There was no difference between Belgian and Italian controls, indicating that dietary habits have no influence on the normal gastroduodenal mast cell number. In CU patients, mast cell numbers were significantly higher: 32.4/HPF (186.0/mm2) in the stomach (P<0.0001) and 44.8/HPF (246.0/mm2) in the duodenum (P=0.0002). CU is thus associated with mast cell infiltration in the gastroduodenal mucosa, even if patients do not have gastrointestinal symptoms. Mast cell counting in gastroduodenal biopsies of CU patients can be useful in selecting patients who may respond to a therapy with intestinal mast-cell-stabilizing agents.

Helicobacter pylori and extragastric diseases--other Helicobacters

The involvement of Helicobacter pylori in the pathogenesis of extragastric diseases continues to be an interesting topic in the field of Helicobacter-related pathology. Although conflicting findings have been reported for most of the disorders, a role of H. pylori seems to be important especially for the development of cardiovascular and hematologic disorders. Previously isolated human and animal Helicobacter sp. flexispira and "Helicobacter heilmannii" strains have been validated using polyphasic taxonomy. A novel enterohepatic Helicobacter has been isolated from mastomys and mice, adding to the list of helicobacters that colonize the liver. Genetic targets that may aid the classification of novel Helicobacter species have emerged. Animal models of Helicobacter-induced gastric and hepatobiliary diseases have offered insights to the mechanisms associated with premalignant transformation.