Blastocystis hominis; Friend or Foe.

<i>Blastocystis hominis (B. hominis)</i> remains the most common parasite identified through stool examination. A clinician will undoubtedly encounter the presence of this parasite numerous times in their career. Thus, it is vital to know if this organism is a 'friend or foe', or in other words, whether it is a commensal or a pathogen. This will help clinicians decide whether to treat or not. This literature review discusses the best available evidence of the association of <i>B. hominis</i> and two diseases- irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). Particularly, focus has been paid to the effect of antimicrobial therapy in improving disease activity/symptoms and concluding on the pathogenicity of <i>B. hominis</i> based on <i>in vitro</i>, observational studies, and randomized controlled trials. Most importantly, the review presents a concise set of recommendations for when and how to treat <i>B. hominis</i> in a patient presenting gastrointestinal ailments.