Hundred years of allergen immunotherapy.

Allergic rhinitis was almost unknown until the early 19th century, but within 100 years it was described as a modern epidemic. Pollen was identified as the likely cause of hayfever and although the nature and mechanisms of the sensitivity remained obscure, it was speculated that hayfever might be caused by a toxin in pollen. Vaccination schedules were developed to treat this, but later it became clear that an antibody was responsible. The first clinical trials of specific immunotherapy (SIT) were published in 1911 and 1914 and were followed by several similar papers from the United States. The use of skin prick tests and new allergen extraction techniques accelerated the development of SIT, which became a widespread practice, especially in the United States. Formal controlled clinical trials were reported in 1953 (United Kingdom) and in 1965 (United States). Since then, many controlled clinical trials have confirmed the efficacy of SIT, and although some concerns have arisen around safety, SIT remains a valid option for treating allergic disease. Recent developments include the introduction of sublingual immunotherapy, and clinical trials of recombinant and peptide vaccines. Future developments should increase efficacy and safety, but the biggest challenge to the wider use of SIT is probably economic, as patients and healthcare providers become increasingly critical of all forms of allergy treatments.