Bacillus Clausii, a commonly used Bacillus spp. probiotic, is a rod-shaped, nonpathogenic, spore-forming, aerobic, gram-positive bacterium. It lives in the soil but is also a natural microbiota of the mammalian gastrointestinal tract. B. Clausii is classified as a probiotic microorganism that maintains a symbiotic relationship with the host organism. Its antimicrobial and immunomodulatory properties support its use for the treatment and prevention of intestinal bacterial flora disorders, with particular efficacy suggested for diarrhea according to clinical trial data and a systematic review and meta-analysis. Small trials have investigated its use for prevention of infection in preterm neonates, treatment of nasal allergies and upper respiratory infections in children, and treatment of acute or chronic diarrhea, small-intestine bacterial overgrowth (SIBO), and adverse effects of Helicobacter pylori therapy in adults1. It is recommended for short periods of time and can be used during pregnancy and lactation and in breastfeeding infants