Reported are the cases of three hydrocephalic patients who developed a clinically heterogenous entity with an allergic rejection of their silicone ventriculoperitoneal shunts. All of the patients had an original presentation indicative of a shunt infection, but laboratory analysis revealed sterile cerebrospinal fluid in all three cases. The typical course included recurrent skin breakdowns over the shunt tract, subsequent infections and development of fungating granulomas. Treatment, with successful resolution of the symptoms, included changing the shunt material from silicone to polyurethane, with immunosuppression in one patient and removal of the shunt altogether in the other two patients. The roles of the immune system and silicone in the pathophysiology of this condition are discussed.