CHICAGO The value of probiotics in atopic disease remains controversial, but clues are beginning to emerge in the literature about probiotics' role in treatment and prevention.
Dr. Sharon S. Raimer highlighted the conflicting trail of evidence surrounding probiotic supplementation for the prevention and treatment of pediatric atopic dermatitis (AD) at a meeting sponsored by the American Academy of Pediatrics.
"It looks like at the present time that probiotics are really not very good for treatment, but they might help in prevention; but you have to give the probiotic prenatally for it to really work," said Dr. Raimer, chair of dermatology, University of Texas at Galveston.
These considerations are largely based on a recent meta-analysis of six prevention and four treatment double-blind randomized controlled trials of probiotics and pediatric AD (J. Allergy Clin. Immunol. 2008;121: 11621).
The analysis identified a significant risk reductionby as much as 61%associated with the use of prenatal and/or postnatal probiotics for primary pediatric AD prevention among 1,581 participants, but only a marginal effect of treatment among 299 participants.
Such meta-analyses are complicated by the variety of bacteria strains and strengths studied, Dr. Raimer said.
Probiotic trials also typically have small sample sizes and heterogeneity of protocols, and might not assess for use of potential confounders such as concomitant antibiotics, topical corticosteroids, and antigen- eliminating diets.
An early trial supporting the role of probiotics in allergy prevention randomized mothers with a family history of atopic eczema, allergic rhinitis, or asthma to two capsules containing placebo or 1 × 1010 colony-forming units of Lactobacillus rhamnosus GG daily for 24 weeks before date of delivery.
After delivery, breastfeeding mothers were given the capsules, while infants who were not breastfed were given the capsule contents mixed with water, for 6 months.
Atopic eczema was diagnosed in 46 of 132 (35%) children at 2 years of age, with the frequency of eczema in the probiotic group half that of the placebo group (23% vs. 46%) (Lancet 2001;357:10769).
A follow-up study of these at-risk children revealed that 14 of 53 (26%) receiving Lactobacillus had developed atopic eczema at 4 years, compared with 25 of 54 (46%) receiving placebo (Lancet 2003;361:186971), suggesting that the preventive effect of Lactobacillus extends beyond infancy. Skin-prick test reactivity was found to be the same in both groups.
Early probiotic supplementation alone appears not to be beneficial in reducing the risk of AD and might actually increase the risk of allergen sensitization in high-risk children, said Dr. Raimer, also a professor of dermatology and pediatrics.
She cited an Australian study that found no difference in AD rates at 6 and 12 months between 177 infants who received Lactobacillus acidophilus or placebo for the first 6 months of life, and a significantly higher rate of sensitization to common allergens in the probiotic group at 12 months (Allergy Clin. Immunol. 2007;119:18491).
Finally, a prospective randomized trial of supplementation during pregnancy and early infancy adds even more intrigue to the probiotic controversy.
Supplementation with 5 × 109 colony-forming units of Lactobacillus GG twice daily for 46 weeks before delivery and 6 months postnatally neither reduced the incidence of atopic eczema nor altered disease severity in AD affected children, but was associated with an increased rate of recurrent episodes of wheezing bronchitis in the study children (Pediatrics 2008;121:e8506).
The German researchers concluded that Lactobacillus GG cannot be generally recommended for primary prevention of atopic eczema.