Probiotics for Kids After Antibiotics

Antibiotics are among the most valuable medical tools in pediatric care, but they disrupt the gut microbiome. Antibiotic-associated diarrhea (AAD) affects roughly 11–40% of children taking antibiotics, with the rate depending on the antibiotic class and the child’s age. Whether giving probiotics during and after a course can reduce this disruption has been tested in dozens of trials — more consistently than for most supplements children are offered.

The Evidence: Lactobacillus rhamnosus GG

Lactobacillus rhamnosus GG (LGG) is the best-studied probiotic strain for preventing pediatric AAD. The most current Cochrane review (Guo et al., 2019; PMID 31039287) pooled 33 trials with 6,352 children and found probiotics cut the risk of AAD from 19% to 8%, a 55% relative reduction (RR 0.45, 95% CI 0.36–0.56). The benefit was much larger when at least 5 billion CFU/day were used: number needed to treat (NNT) of 6, versus 9 overall. LGG and Saccharomyces boulardii were the strains with the strongest individual evidence.

The Evidence: Saccharomyces boulardii

Saccharomyces boulardii is a yeast, not a bacterium, so antibiotics do not kill it. That makes it practical during an antibiotic course — timing relative to each dose is not critical. Pediatric trials show S. boulardii (250–500 mg/day) reduces AAD by roughly 40–50%, in line with LGG. Some pediatric guidelines (including the European Society for Paediatric Gastroenterology, Hepatology and Nutrition, ESPGHAN) specifically endorse LGG and S. boulardii as the strains with the strongest evidence.

Timing and Dosing

Start the probiotic at the same time as the antibiotic, not after symptoms appear. Continue for at least 1–2 weeks after the antibiotic course ends. For bacterial strains like LGG, space the dose at least 2 hours apart from the antibiotic so the antibiotic is less likely to kill it. S. boulardii can be taken at the same time as the antibiotic. Effective trial doses: LGG at 5–10 billion CFU/day; S. boulardii at 250–500 mg/day.

Safety

Across the 2019 Cochrane review (24 trials reporting safety data), no serious adverse events were attributed to probiotics in otherwise healthy children. Probiotics are not appropriate for severely ill, immunocompromised, or central-line-dependent children, where rare bloodstream infections from probiotic strains have been reported.

Longer-Term Microbiome Recovery

Beyond AAD prevention, broader microbiome disruption from antibiotic courses in children can persist for weeks to months. Fermented foods — yogurt with live cultures, kefir — provide a wider mix of microbes than single-strain capsules. A diet high in prebiotic fiber (fruits, vegetables, legumes) supports regrowth of beneficial species. These dietary steps complement the probiotic course.