Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Delusional infestation: Epidemiology, clinical presentation, assessment and diagnosis

Kathryn N Suh, MD, FRCPC
Jay S Keystone, MD, MSc (CTM), FRCPC
Section Editor
Stephen Marder, MD
Deputy Editors
Richard Hermann, MD
Abena O Ofori, MD


Delusional infestation (also called delusional parasitosis) is a rare disorder in which affected individuals have the fixed, false belief (delusion) that they are infected by "bugs": parasites, worms, bacteria, mites, or other living organisms. As with all delusions, this belief cannot be corrected by reasoning, persuasion, or logical argument. Many affected individuals are quite functional; for the minority, delusions of parasitic infection may interfere with usual activities [1].

Delusional infestation is a delusional disorder of the somatic type [2], a subgroup of delusional disorders in which nonexistent disease or alteration of the body forms the basis of the disorder. Delusions of infestation are the most common form of monosymptomatic hypochondriacal psychosis; others include delusions of dysmorphism and delusions of body odor or halitosis.

This topic addresses the epidemiology, clinical presentation, and diagnosis of delusional infestation. Treatment of delusional infestation is discussed separately. Other psychotic disorders are discussed separately. First and second-generation antipsychotic drugs are discussed separately. (See "Treatment of delusional infestation" and "Brief psychotic disorder" and "Postpartum psychosis: Epidemiology, pathogenesis, clinical manifestations, course, assessment, and diagnosis" and "Schizophrenia in adults: Clinical manifestations, course, assessment, and diagnosis" and "Pharmacotherapy for schizophrenia: Acute and maintenance phase treatment" and "First-generation antipsychotic medications: Pharmacology, administration, and comparative side effects" and "Second-generation antipsychotic medications: Pharmacology, administration, and side effects".)


Delusional infestation — Delusional infestation is known by numerous other names, including Ekbom syndrome, delusory parasitosis, psychogenic parasitosis, delusional parasitosis, delusional ectoparasitosis, formication, chronic tactile hallucinosis, dermatophobia, parasitophobia, and cocaine bugs. The principal name for the disorder through approximately 2015 "delusional parasitosis" was introduced in 1948 in a description of 45 cases [3]. More recent literature refers to delusional infestation [4].

Two forms of delusional infestation are widely recognized [5,6]:

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Nov 02, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Lynch PJ. Delusions of parasitosis. Semin Dermatol 1993; 12:39.
  2. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), American Psychiatric Association, Arlington 2013.
  3. Wilson JW, Miller HE. Delusions of parasitosis. Arch Dermatol Syphilol 1946; 54:39.
  4. Bewley AP, Lepping P, Freudenmann RW, Taylor R. Delusional parasitosis: time to call it delusional infestation. Br J Dermatol 2010; 163:1.
  5. Musalek M, Bach M, Passweg V, Jaeger S. The position of delusional parasitosis in psychiatric nosology and classification. Psychopathology 1990; 23:115.
  6. Freinhar JP. Delusions of parasitosis. Psychosomatics 1984; 25:47.
  7. Hylwa SA, Foster AA, Bury JE, et al. Delusional infestation is typically comorbid with other psychiatric diagnoses: review of 54 patients receiving psychiatric evaluation at Mayo Clinic. Psychosomatics 2012; 53:258.
  8. Pearson ML, Selby JV, Katz KA, et al. Clinical, epidemiologic, histopathologic and molecular features of an unexplained dermopathy. PLoS One 2012; 7:e29908.
  9. Kellett CE. Sir Thomas Browne and the disease called the Morgellons. Ann Med Hist 1935; 7:467.
  10. Thibierge G. Les acaraphobes. Rev Gén Clin Thér 1894; 8:373.
  11. Koblenzer CS. The challenge of Morgellons disease. J Am Acad Dermatol 2006; 55:920.
  12. Middelveen MJ, Bandoski C, Burke J, et al. Exploring the association between Morgellon’s disease and Lyme disease: identification of Borrelia burgorferi in Morgellons disease patients. BMC Dermatol 2015; 15:1.
  13. Middelveen MJ, Mayne PJ, Kahn DG, Stricker RB. Characterization and evolution of dermal filaments from patients with Morgellons disease. Clin Cosmet Investig Dermatol 2013; 6:1.
  14. Middelveen MJ, Burugu D, Poruri A, et al. Association of spirochetal infection with Morgellons disease. F1000Res 2013; 2:25.
  15. Lyell A. The Michelson Lecture. Delusions of parasitosis. Br J Dermatol 1983; 108:485.
  16. Bailey CH, Andersen LK, Lowe GC, et al. A population-based study of the incidence of delusional infestation in Olmsted County, Minnesota, 1976-2010. Br J Dermatol 2014; 170:1130.
  17. Melton LJ 3rd. History of the Rochester Epidemiology Project. Mayo Clin Proc 1996; 71:266.
  18. Hsiao MC, Liu CY, Yang YY, Yeh EK. Delusional disorder: retrospective analysis of 86 Chinese outpatients. Psychiatry Clin Neurosci 1999; 53:673.
  19. Trabert W. 100 years of delusional parasitosis. Meta-analysis of 1,223 case reports. Psychopathology 1995; 28:238.
  20. Foster AA, Hylwa SA, Bury JE, et al. Delusional infestation: clinical presentation in 147 patients seen at Mayo Clinic. J Am Acad Dermatol 2012; 67:673.e1.
  21. Reilly TM, Batchelor DH. The presentation and treatment of delusional parasitosis: a dermatological perspective. Int Clin Psychopharmacol 1986; 1:340.
  22. Munro A. Monosymptomatic hypochondriacal psychosis manifesting as delusions of parasitosis. A description of four cases successfuly treated with pimozide. Arch Dermatol 1978; 114:940.
  23. Reilly TM. Monosymptomatic hypochondriacal Psychosis: Presentation and Treatment. Proc R Soc Med 1977; 70:39.
  24. Skott A. Delusions of infestation. In: Report from the Psychiatric Research Centre, No. 13, St. Jörgen's Hospital, University of Göteborg, Göteborg, Sweden 1978.
  25. Barsky AJ, Borus JF. Functional somatic syndromes. Ann Intern Med 1999; 130:910.
  26. Huber M, Kirchler E, Karner M, Pycha R. Delusional parasitosis and the dopamine transporter. A new insight of etiology? Med Hypotheses 2007; 68:1351.
  27. Bhatia MS, Jagawat T, Choudhary S. Delusional parasitosis: a clinical profile. Int J Psychiatry Med 2000; 30:83.
  28. Zanol K, Slaughter J, Hall R. An approach to the treatment of psychogenic parasitosis. Int J Dermatol 1998; 37:56.
  29. The matchbox sign. Lancet 1983; 2:261.
  30. Trabert W. Shared psychotic disorder in delusional parasitosis. Psychopathology 1999; 32:30.
  31. Musalek M, Kutzer E. The frequency of shared delusions in delusions of infestation. Eur Arch Psychiatry Neurol Sci 1990; 239:263.
  32. Gill CJ, Hamer DH. "Doc, there's a worm in my stool": Munchausen parasitosis in a returning traveler. J Travel Med 2002; 9:330.
  33. Schwartz E, Witztum E, Mumcuoglu KY. Travel as a trigger for shared delusional parasitosis. J Travel Med 2001; 8:26.
  34. Driscoll MS, Rothe MJ, Grant-Kels JM, Hale MS. Delusional parasitosis: a dermatologic, psychiatric, and pharmacologic approach. J Am Acad Dermatol 1993; 29:1023.
  35. Wykoff RF. Delusions of parasitosis: a review. Rev Infect Dis 1987; 9:433.
  36. Oruc L, Bell P. Multiple rape trauma followed by delusional parasitosis. A case report from the Bosnian war. Schizophr Res 1995; 16:173.
  37. Pope FM. Parasitophobia as the presenting symptom of vitamin B12 deficiency. Practitioner 1970; 204:421.
  38. ALESHIRE I. Delusion of parasitosis: report of successful care with antipellagrous treatment. J Am Med Assoc 1954; 155:15.
  39. Nagaratnam N, O'Neile L. Delusional parasitosis following occipito-temporal cerebral infarction. Gen Hosp Psychiatry 2000; 22:129.
  40. Blasco-Fontecilla H, Bragado Jiménez MD, García Santos LM, Barjau Romero JM. Delusional disorder with delusions of parasitosis and jealousy after stroke: treatment with quetiapine and sertraline. J Clin Psychopharmacol 2005; 25:615.
  41. Kumbier E, Kornhuber M. [Delusional ectoparasitic infestation in multiple system atrophy]. Nervenarzt 2002; 73:380.
  42. Floris G, Cannas A, Melis M, et al. Pathological gambling, delusional parasitosis and adipsia as a post-haemorrhagic syndrome: a case report. Neurocase 2008; 14:385.
  43. May WW, Terpenning MS. Delusional parasitosis in geriatric patients. Psychosomatics 1991; 32:88.
  44. Berrios GE. Delusional parasitosis and physical disease. Compr Psychiatry 1985; 26:395.
  45. Alciati A, Fusi A, D'Arminio Monforte A, et al. New-onset delusions and hallucinations in patients infected with HIV. J Psychiatry Neurosci 2001; 26:229.
  46. Slaughter JR, Zanol K, Rezvani H, Flax J. Psychogenic parasitosis. A case series and literature review. Psychosomatics 1998; 39:491.
  47. Aizenberg D, Schwartz B, Zemishlany Z. Delusional parasitosis associated with phenelzine. Br J Psychiatry 1991; 159:716.
  48. Liebowitz MR, Nuetzel EJ, Bowser AE, Klein DF. Phenelzine and delusions of parasitosis: a case report. Am J Psychiatry 1978; 135:1565.
  49. Finkelstein E, Amichai B, Halevy S. Paranoid delusions caused by ketoconazole. Int J Dermatol 1996; 35:75.
  50. Swick BL, Walling HW. Drug-induced delusions of parasitosis during treatment of Parkinson's disease. J Am Acad Dermatol 2005; 53:1086.
  51. Steinert T, Studemund H. Acute delusional parasitosis under treatment with ciprofloxacin. Pharmacopsychiatry 2006; 39:159.
  52. Robaeys G, De Bie J, Van Ranst M, Buntinx F. An extremely rare case of delusional parasitosis in a chronic hepatitis C patient during pegylated interferon alpha-2b and ribavirin treatment. World J Gastroenterol 2007; 13:2379.
  53. Fleury V, Wayte J, Kiley M. Topiramate-induced delusional parasitosis. J Clin Neurosci 2008; 15:597.