Probiotics for the treatment or prevention of atopic dermatitis - A review of the evidence from randomized controlled trials

Probiotics are defined as live microorganisms which, when administered in adequate amounts, confer a health benefit on the host. To synthesize the evidence for the effectiveness of probiotics in the treatment or prevention of atopic dermatitis (AD) in children, we reviewed the results of 13 relevant randomized (placebo)-controlled trials (RCTs), 10 of which evaluated probiotics as treatment and 3 for prevention of AD. The main outcome measure in 9 RCTs was the change in SCORAD (SCORing Atopic Dermatitis). Four RCTs suggested that there was a statistically significant decrease in SCORAD after probiotic administration to infants or children with AD for 1 or 2 months compared with that after placebo, while in two RCTs SCORAD was significantly reduced after treatment with lactobacilli only in children with IgE-associated AD. In four of these six RCTs, clinical improvement was associated with a change in some inflammatory markers. In three RCTs, the change in SCORAD was not statistically significant between probictic- and placebo-treated children, although in one of these trials SCORAD was significantly lower after probiotic than with placebo treatment in food-sensitized children. In most RCTs, probiotics did not cause a statistically significant change in interferon-gamma, interleukin-4, tumor necrosis factor-alpha, eosinophil cationic protein or transforming growth factor-beta compared with placebo. Regarding the effectiveness of probiotics in the prevention of AD, in two RCTs, infants at high risk for atopy who received probiotics developed AD significantly less frequently during the first 2 years of life than infants who received placebo. In these studies, mothers were administered Lactobacillus rhamnosus GG with or without other probiotics perinatally, followed by treatment of the infants with the same probiotics for the first 6 months of life. However, in another trial, neither the frequency nor the severity of AD during the first year of life were significantly different between infants with atopic mothers who received L. acidophilus for the first 6 months of life compared with infants who received placebo. Probiotics, especially L. rhamnosus GG, seem to be effective for the prevention of AD. They were also found to reduce the severity of AD in approximately half of the RCTs evaluated, although they were not found to change significantly most of the inflammatory markers measured in the majority of the RCTs evaluated. More RCTs need to be conducted to elucidate whether probiotics are useful for the treatment or prevention of AD.