Development of asthma
Seven studies aimed to investigate whether AIT is able to prevent the occurrence of asthma in patients suffering from AR during the full analysis and/or follow-up period (15,17–19,21,22,25,26). Most assessments indicated that the risk of incident asthma was significantly lower in patients with AR exposed to AIT compared with that in the Non-AIT group regardless of the type of AIT (SCIT or SLIT), the preparation studied (allergoid or natural allergen preparation), or the type of allergen (HDM, birch or grass pollen, all allergens) for up to 9 years follow-up. Nevertheless, the results were not constantly significant at certain analytical time periods (19,22), for single preparations or preparation groups (22,26) or for the age group of children (15). The only study comparing the risk in adults and children/adolescents did not show a significant difference for follow-up and full analysis periods (21). For details see tables S5, S6, S7, S8 in supplementary information.