Seven randomised double-blind, placebo-controlled trials (256 children: 129 and 127 receiving SLAV and placebo, respectively) were included in the review.
Symptom scores.
Symptom reductions were observed for rhinitis (SMD -0.44, 95% CI: -1.22, 0.3, P=0.27) in 6 studies and for conjunctivitis (SMD -1.49, 95% CI: -3.69, 0.72, P=0.19) in 2 studies. A statistically significant reduction was reported for asthma (SMD -1.42, 95% CI: -2.51, -0.34, P=0.010) in 5 studies. The sensitivity analysis (using a fixed-effect model) confirmed the magnitude of these findings. Details were given in the paper.
Medication requirement scores.
The pooled results from 4 studies indicated a reduction in drug dosage (SMD -1.01, 95% CI: -2.06, 0.04, P=0.06). This finding was confirmed in a sensitivity analysis. Details were given in the paper.
Other outcomes.
All studies considered safety aspects of the intervention and no serious or systemic reactions were reported. Minor side-effects (local swelling or gastrointestinal) were experienced in some children receiving the active treatment. Further details were given in the paper.
The limited results for skin reactivity showed a reduction in 4 studies and no change in a fifth study. Serum IgE levels were not modified in any of the 4 studies, while IgG levels were increased in only 2 of the 5 studies that measured them.