Eleven studies involving 426 patients were included.
Immunotherapy for house dust mite:
significant heterogeneity was found across studies with respect to symptomatic benefit (p<0.05).
OR for symptomatic improvement 2.7 (95% confidence interval, CI: 1.7, 4.4);
OR for reduction in medication 4.2 (95% CI: 2.2, 7.9);
OR for reduction in bronchial hyper-reactivity 13.7 (95% CI: 3.8, 50).
Immunotherapy for other allergens:
OR for symptomatic improvement 4.8 (95% CI: 2.3, 10.1);
OR for reduction in bronchial hyper-reactivity 5.5 (95% CI: 2.8, 10.7).
Overall effect of immunotherapy:
symptomatic improvement, OR 3.2 (95% CI: 2.2, 4.9), significant heterogeneity (p<0.05); reduction in bronchial hyper-reactivity, OR 6.8 (95% CI: 3.8, 12.0); the mean effect size for any allergen immunotherapy on all continuous outcomes was 0.71 (95% CI: 0.43, 1.00), which corresponded to a mean 7.1% predicted improvement in the forced expiratory volume in 1 second (FEV1) from immunotherapy.
Side-effects of immunotherapy:
systematic reactions, 32% (95% CI: 20%, 44%) of patients receiving immunotherapy as compared with 18% (95% CI: 7%, 29%) of patients receiving placebo.