Context

Asthma affects millions of people worldwide. Current drug treatments for asthma relieve bronchospasm and airway inflammation but do not offer a cure, and symptoms return when treatment is stopped. In many parts of the world, allergen-specific immunotherapy is used to treat asthma; it is the only treatment option that targets the underlying disease process, by modulating the immune response. However, immunotherapy can induce severe adverse reactions including anaphylaxis and death, especially in people with asthma, which has led to restrictions on its use, particularly in the UK.1 In a previous systematic review, Abramson and colleagues2 included 75 trials of allergen immunotherapy in asthma published between 1954 and 2001. This review concluded that immunotherapy significantly reduced asthma symptoms, medication requirements and bronchial hypersensitivity. The authors have now updated their analysis, including 13 new trials published between 2001 and 2005.