Eighteen studies were included: seven prevention (n=2,197) and 11 treatment (n=712) studies that met the inclusion criteria. Seven RCTs assessed prevention and 11 RCTs assessed treatment of atopic dermatitis, although the authors stated that 12 studies assessed treatment. Six of the seven studies that assessed prevention were level A2 and one was level B. Seven of the 11 treatment studies were level A2 evidence.
Results on use of probiotics in prevention of atopic dermatitis were mixed. One study reported a 50% reduction in the incidence of atopic dermatitis compared to placebo and another study showed no reduction. One study showed that only one strain of probiotics reduced incidence of atopic dermatitis.
Treatment of atopic dermatitis with probiotics showed conflicting results: four studies demonstrated reduction of SCORAD score and three studies showed no effect on atopic dermatitis, but did show a significantly modest SCORAD score with IgE-associated atopic dermatitis.
The one double-blind RCT conducted so far showed that incidence of atopic dermatitis was significantly lower in prebiotics group than the placebo group (9.8% versus 23.1%). A large proportion (>20%) of the infants were lost to follow-up during the intervention period. Four studies reported no effect on the severity of atopic dermatitis in any group.
The one study that investigated the use of synbiotics for the treatment of atopic dermatitis showed a significant improvement, but synbiotics did not appear to be superior to prebiotics alone.
Two studies that assessed the effect of probiotics on food allergies as a secondary outcome did not find any difference in incidence.