Blastocystis hominis is one of the most common parasites present in the human gastrointestinal tract. Transmission usually occurs via food and water contaminated with cystic forms or via the faecal-oral route. The prevalence of infection is approximately 30–50% in developing countries and about 1.5–10% in developed ones. Blastocystis hominis was long considered as a large intestine commensal due to asymptomatic infestation, possibly characterised by temporary or permanent gastrointestinal carrier state, in some cases. Currently, this protozoan is considered pathogenic as symptoms develop in the course of infestation, especially in infected immunocompromised individuals. The importance of Blastocystis hominis as a factor responsible for enteral and parenteral symptoms is underestimated in clinical practice, and the infestation with this parasite is underdiagnosed. We present a case of a 5-year-old boy infected with Blastocystis hominis, who developed gastrointestinal symptoms and urticaria.