The paper reports on four atypical cases of blastocystosis with prevalence of digestive and cutaneous disorders and of the allergic and general phenomena. The diagnosis could be established only after revealing Blastocystis hominis in the fecal parasitologic examination. The disappearance, in all the four cases, of varied clinical, delayed signs after treatment with metronidazol and stamycine (in two or even four repeated treatment schedules at 10 days' interval) is the proof that Bl. hominis might be the agent (unique or associated with other parasites) of some polymorphous disorders. Our findings are a call to specialists and clinicians for investigating the parasite and using an adequate treatment.