Best Probiotics for Traveler's Diarrhea (2026): S. boulardii Evidence
The best probiotic for traveler’s diarrhea is Florastor: its label names S. boulardii CNCM I-745, the best-studied probiotic for traveler’s diarrhea, at $1.93 a day for 2 capsules at the brand’s price. It keeps at room temperature, so it travels well.
By Erin Rose Updated October 19, 2026 How we rank
Brand prices, checked October 19, 2026.
Our pick for: Most travelers
Florastor
First of the 3 we compare: the only one here whose label names the strain from the travel trials
- Strain
- S. boulardii CNCM I-745The strain in the trials
- Amount
- 250 mg a capsuleLabel: 2 capsules, 1 to 2 times a day
- A day
- $1.932 capsules; $3.86 at 4
- Bottle
- 30 capsules$28.97 at the brand, 15 days at 2 a day
- Storage
- Room temperatureNo fridge on the road
- Form
- A yeast, not a bacteriumAntibiotics for bacteria do not kill it
Why we pick it Its label names CNCM I-745, the strain behind the travel results. Each capsule holds 250 mg; the largest trial gave 250 mg or 1,000 mg a day, so 1 or 4 capsules.
What you give up It costs more than other S. boulardii. Those labels do not name a strain, so we cannot tie them to the trials.
Which probiotic is right for you?
Buy S. boulardii, a probiotic yeast. Here is how to save, and what to do about medicine.
Want to spend less?
Jarrow’s S. boulardii has 250 mg (5 billion CFU) a capsule, plus 200 mg of MOS, a fiber from yeast. Two capsules cost $0.57 at the brand’s price, against $1.93 for Florastor. The catch: its label does not name the strain, and the trials used CNCM I-745.
Jarrow Saccharomyces Boulardii + MOS
$0.57 for 500 mg (2 capsules)
Taking antibiotics or travel medicine?
S. boulardii is a yeast, so antibiotics made for bacteria do not kill it. Trials have given it alongside antibiotics to lower the risk of antibiotic diarrhea. Antifungal medicine can kill it, so do not take the two together. Ask the clinic that prescribed your medicine about anything else you plan to take.
Thinking of a bacterial probiotic?
In the 2019 review, LGG showed a trend that fell short of proof, and L. acidophilus alone did not help. An older review also found a mix of L. acidophilus and B. bifidum helped (McFarland 2007). Schiff Digestive Advantage (B. coagulans) keeps well on the road, but it has not been tested for traveler’s diarrhea.
Probiotics for travel we compared, ranked
S. boulardii first, then other probiotics sold for travel. Costs are a day at each brand’s own price: 2 capsules (500 mg) of S. boulardii, or 1 capsule of Schiff, priced from a 60-capsule bottle at Vitacost because the brand has no store.
| Probiotic | Cost a day | Why it is or is not a pick |
|---|---|---|
| FlorastorS. boulardii CNCM I-745, 2 capsules | $1.93 | Our pick: the trial strain, 250 mg a capsule |
| Jarrow Saccharomyces Boulardii + MOSS. boulardii, 2 capsules | $0.57 | S. boulardii for less; the label names no strain |
| Schiff Digestive AdvantageB. coagulans GBI-30, 1 capsule | $0.36 | B. coagulans, not studied for traveler’s diarrhea |
What the trials found
A 2019 review pooled the travel trials of probiotics that had been tested at least twice. S. boulardii CNCM I-745 lowered the risk of traveler’s diarrhea by about a fifth. Of the three it could pool (S. boulardii, LGG and L. acidophilus), it was the only one that clearly worked (McFarland 2019).
The largest trial gave about 3,000 Austrian travelers 250 mg or 1,000 mg of S. boulardii a day, or a placebo. Fewer of them got diarrhea. The effect was stronger at the higher dose and in people who took it every day, and it seemed strongest on trips to North Africa and Turkey (Kollaritsch 1993).
The CDC’s travel guide says the data are not yet enough to recommend probiotics for travelers. It points to bismuth subsalicylate (Pepto-Bismol), which cut traveler’s diarrhea by about half in studies in Mexico. A 2022 review also found that rifaximin, a prescription antibiotic, prevented it better than probiotics (Fan 2022). So S. boulardii lowers the odds a little; it does not make you safe from bad food or water.
How to take it
Florastor’s label says 2 capsules, once or twice a day. Each capsule has a little lactose (32.5 mg). It has not been tested in pregnancy, so ask your doctor first if you are pregnant (Dugoua 2009). Skip it, or ask your doctor first, if you are seriously ill or your immune system is weak: rare blood infections with probiotic yeast have been reported in people who were already ill (Hempel 2011).
See a doctor if you have a high fever, blood in your stool, or diarrhea that lasts more than a few days. A probiotic does not treat traveler’s diarrhea once it starts; drink fluids with oral rehydration salts.
Questions people ask
When should I start taking probiotics before traveling?
The trials gave S. boulardii to prevent illness, so start before or on the day you leave and take it every day of the trip. In the largest trial, it worked best in people who took it every day.
Do I need a refrigerated probiotic for travel?
No. Both S. boulardii products here keep at room temperature. Keep the bottle out of heat, such as a hot car.
What is the best probiotic for Mexico/India/Southeast Asia travel?
No trial looked at those places on their own, so the advice is the same for any trip where the water is not safe: S. boulardii every day, plus care with food and water.
What else should I pack for travel gut health?
Oral rehydration salts, in case you get sick. Drink bottled or treated water and skip ice, raw salads and undercooked food where the water is not safe. Ask a travel clinic whether you need medicine for the trip.
How we rank
Three things, in order: is the product the kind that worked in travel trials (S. boulardii); does its label name the strain from those trials; and what a day costs at the brand’s own price. No product here is on a testing list we check. We don’t score probiotics out of 10; dose depends on the strain. More on our method.
Sources
- McFarland LV, Goh S. “Are probiotics and prebiotics effective in the prevention of travellers’ diarrhea: A systematic review and meta-analysis.” Travel Med Infect Dis. 2019. PubMed 30278238
- Kollaritsch H, et al. “Prevention of traveler’s diarrhea with Saccharomyces boulardii. Results of a placebo controlled double-blind study” (in German). Fortschr Med. 1993. PubMed 8486328
- McFarland LV. “Meta-analysis of probiotics for the prevention of traveler’s diarrhea.” Travel Med Infect Dis. 2007. PubMed 17298915
- Szajewska H, Kołodziej M. “Systematic review with meta-analysis: Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea.” Aliment Pharmacol Ther. 2015. PubMed 26216624
- Fan H, et al. “Probiotics and rifaximin for the prevention of travelers’ diarrhea: A systematic review and network meta-analysis.” Medicine (Baltimore). 2022. PubMed 36221413
- Dugoua JJ, et al. “Probiotic safety in pregnancy: a systematic review and meta-analysis of randomized controlled trials of Lactobacillus, Bifidobacterium, and Saccharomyces spp.” J Obstet Gynaecol Can. 2009. PubMed 19646321
- CDC Yellow Book, “Travelers’ Diarrhea” (probiotics and bismuth subsalicylate for prevention). cdc.gov
- Hempel S, et al. “Safety of probiotics used to reduce risk and prevent or treat disease.” Evid Rep Technol Assess. 2011. PubMed 23126627
- Florastor label (250 mg S. boulardii CNCM I-745 a capsule): NIH Dietary Supplement Label Database, label 206744. Brand pages and labels, read October 19, 2026: Florastor, Jarrow Formulas; Schiff at Vitacost.