Fourteen randomised controlled trials (RCTs) were included in the review. Thirteen RCTs (3,092 infants) assessed atopic dermatitis. Ten RCTs (2,711 infants) assessed immunoglobulin E-associated atopic dermatitis. There were insufficiently detailed data (11 trials) to assess severity of dermatitis. All trials were double-blinded and none showed differences in drop-outs between treatment and placebo groups. However, drop-out rates were over 20% in half the trials. Assessment was at between one and seven years of age; most used a follow-up period of one or two years. All except two trials reported outcome assessment by clinicians or trial personnel.
Children in the probiotic treatment groups had lower rates of atopic dermatitis than those in the placebo groups (RR 0.79, 95% CI 0.71 to 0.88; Ι²=24%; 13 RCTs; fixed-effect model). This was statistically significant with low levels of inconsistency between trials. A random-effects analysis did not materially alter the result; sensitivity analyses excluding trials with looser diagnostic criteria also did not change the estimate.
The evidence for a reduction in immunoglobulin E-associated atopic dermatitis was less clear. A fixed-effect analysis showed a statistically significant benefit with low levels of inconsistency (RR 0.80, 95% CI 0.66 to 0.96; Ι²=32%; 10 RCTs). However, the effect did not remain statistically significant in a random-effects analysis (RR 0.83, 95% CI 0.65 to 1.06).
Stratified analyses did not detect meaningful differences between subgroups. A larger estimate of effect in children with no family history of allergic diseases was based on only two trials.
There was no evidence of publication bias.