In all, 88 trials were included, of which 13 were new trials. These trials included 42 that looked at immunotherapy for house mite allergy and six that looked at multiple allergens. Their results were as follows:
Concealment of allocation was assessed as clearly adequate in only 16 of these trials. Significant heterogeneity was present in a number of comparisons. Overall, there was a significant reduction in asthma symptoms and medication, and improvement in bronchial hyper-reactivity following immunotherapy. There was a significant improvement in asthma symptom scores (standardized mean difference -0.59, 95% confidence interval -0.83 to -0.35) and it would have been necessary to treat three patients (95% CI 3 to 5) with immunotherapy to avoid one deterioration in asthma symptoms. Overall it would have been necessary to treat four patients (95% CI 3 to 6) with immunotherapy to avoid one requiring increased medication. There was no consistent effect on lung function. If 16 patients were treated with immunotherapy, one would be expected to develop a local adverse reaction. If nine patients were treated with immunotherapy, one would be expected to develop a systemic reaction (of any severity).
The authors conclude that immunotherapy is effective in asthma albeit there is a risk for local or systemic adverse effects (such as anaphylaxis). This indicates that immunotherapy in asthma should be prescribed by specialists and administered with care, in particular in patients with asthma.