[Etiological diagnosis and treatment of chronic urticaria]

Urticaria is a muco-cutaneous illness which is characterized by a dermal or hypodermal oedema due to a vasodilatation attributed to the release of histamine by mast cells and basophils. Urticaria is a very common complaint, since among 20% of the population will experience at least one episode of urticaria during their life. Chronic urticaria by definition is daily and has persisted for at least six weeks. By contrast with acute urticaria, its etiological and therapeutic approaches can present a significant challenge, leadind to repeated examinations.

Questioning and clinical examination are essential for the etiological diagnosis of chronic urticaria, because they are able to lead rapidly to the suspicion of several causes which can be eradicated to treat the symptoms. If no cause is found, further investigations may be required. Recent studies have shown the lack of profitability of exhaustive laboratory investigations. Thus, many authors at present time advise minimal and non expensive investigations which are determinated by anamnestic data. But most often, the etiology of urticaria remains unknown and this situation leads to the diagnosis of chronic idiopathic urticaria. The treatment of chronic urticaria is above all based on the elimination of the symptoms, either on a specific fashion if the etiological diagnosis is already known, or in a non specific way. The anti-H1 agents are the medications of choice for first line treatment.

Pathophysiology of chronic urticaria is to date well established. As the mechanisms responsible for chronic urticaria are better defined, more therapeutic agents, which are effective on other targets than histamine, should become available. Moreover, recent advances have supported the notion that an underlying autoimmune process could account for many cases of chronic "idiopathic" urticaria. In such severe and refractory urticaria, immunomodulation therapy may bring about clinical improvement.