Probiotics — live microorganisms that, when administered in adequate amounts, confer a health benefit on the host — have been widely investigated as adjunctive or stand-alone therapy for gastrointestinal (GIT) infections. This narrative review synthesises evidence from systematic reviews, meta-analyses, large randomised controlled trials, and clinical guidelines on probiotic use in acute infectious diarrhoea, antibiotic-associated diarrhoea (AAD), Clostridioides difficile-associated diarrhoea (CDAD), Helicobacter pylori infection, and traveller's diarrhoea. Relevant literature was identified through PubMed, the Cochrane Library, and Google Scholar. Pooled evidence indicates that selected strains — particularly Lactobacillus rhamnosus GG and Saccharomyces boulardii — can reduce the duration and severity of acute diarrhoea and lower the incidence of AAD and CDAD, while multi-strain formulations modestly improve H. pylori eradication rates and reduce therapy-related adverse effects. However, an updated 2020 Cochrane review and two large paediatric emergency-department trials have tempered earlier optimism, underscoring strain specificity, dosing, timing, and publication bias as major sources of heterogeneity. Probiotic supplementation appears safe in immunocompetent populations and offers measurable, though strain- and indication-dependent, benefit, supporting cautious, evidence-guided clinical use.