This is a case report of hypochondrical paranoia in a young man, who was convinced of a toxic infection by fungi following mold growth exposure. The patient was admitted to a psychiatric facility, severely pained by the delusional perception of his insides being eaten by fungus. He had undergone a thorough medical examination without the discovery of any somatic irregularities and had attempted to treat himself several times. After four months of hospitalization and the prescription of antipsychotic treatment, he was in recovery. Mild delusions persisted but were no longer pathologically painful.