Delusional infestation (DI) is a rare but disabling psychiatric disorder in which patients are convinced they are infested with parasites or other (non-)living organisms, despite the absence of medical evidence. The condition causes severe psychological distress, social isolation, and a markedly reduced quality of life. Patients often present to dermatologists, but effective management requires close collaboration with psychiatry.This thesis explores the clinical variation within DI, the organizational and communicative barriers to care, and strategies for more harmonized and patient-centered management. The findings show that the itch experienced in DI is not associated with immunological abnormalities, suggesting a perceptual rather than inflammatory origin. Triggers such as post-scabies itch, dopaminergic medication, and stimulant use (e.g., cocaine and amphetamines) may precipitate or exacerbate symptoms.The therapeutic section demonstrates that loss to follow-up and poor adherence are common, often related to limited illness insight and mistrust. Moral case deliberation revealed that direct confrontation with delusional beliefs is usually counterproductive; instead, a gradual, symptom-focused approach fosters trust and collaboration.An international survey highlighted major differences in clinical practice across Europe. A subsequent Delphi consensus study established core diagnostic criteria, a stepwise treatment pathway, and recommendations for collaboration between dermatology and psychiatry.In summary, this thesis shows that DI represents a clinical spectrum in which somatic and psychological factors converge, and that effective care requires integration, standardization, and empathic communication
