Delusional parasitosis

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Delusional parasitosis
Classification and external resources
ICD-10 F22
DiseasesDB 9622
eMedicine derm/939

Delusional parasitosis, also known as delusional infestation[1] or Ekbom's syndrome,[2][3] is a delusional disorder in which individuals incorrectly believe they are infested with parasites, insects, or bugs, whereas in reality no such infestation is present.[4] Individuals with delusional parasitosis usually report tactile hallucinations known as formication, a sensation resembling insects crawling on or under the skin.

Delusional parasitosis is a mental disorder characterized by a fixed, false belief that a skin infestation exists, which is in contrast to cases of actual parasitosis, such as scabies and infestation with Demodex, in which a skin infestation is present and identifiable by a physician through physical examination or laboratory tests.[5][6]

The alternative name, Ekbom's syndrome, was named after Swedish neurologist Karl-Axel Ekbom,[7] who published seminal accounts of the disease in 1937 and 1938. It is differentiated from Willis-Ekbom Disease (WED), another name for restless legs syndrome.

Signs and symptoms[edit]

Details of delusional parasitosis vary among sufferers, it manifests as a crawling and pin-pricking sensation, but it is most commonly described as involving perceived parasites crawling upon or burrowing into the skin, sometimes accompanied by an actual physical sensation (known as formication; often associated with menopause, or sometimes exposure to household cleaning products).[4][8] Sufferers may injure themselves in attempts to be rid of the "parasites". Some are able to induce the condition in others through suggestion, in which case the term folie à deux may be applicable.[3][9]

Nearly any marking upon the skin, or small object or particle found on the person or his clothing, can be interpreted as evidence for the parasitic infestation, and sufferers commonly compulsively gather such "evidence" and then present it to medical professionals when seeking help.[4] This presentation of "evidence" is known as "the matchbox sign" because the "evidence" is frequently presented in a small container, such as a matchbox.[3]

A study conducted of 108 patients at the Mayo Clinic was published in Archives of Dermatology on May 16, 2011. The study failed to find evidence of skin infestation despite doing skin biopsies and examining specimens provided by the patients. The study, which was conducted between 2001 and 2007, concluded that the feeling of skin infestation was delusional parasitosis.[10][11]

Delusional parasitosis is seen more commonly in women, and the frequency is much higher past the age of 40.[3][12]

Delusory cleptoparasitosis is a form of delusion of parasitosis where the person believes the infestation is in their dwelling, rather than on or in their body.[13]


Delusional parasitosis is divided into primary, secondary functional, and secondary organic groups.[14]


In primary delusional parasitosis, the delusions comprise the entire disease entity: there is no additional deterioration of basic mental functioning or idiosyncratic thought processes. The parasitic delusions consist of a single delusional belief regarding some aspect of health. This is also referred to as "monosymptomatic hypochondriacal psychosis",[15] and sometimes as "true" delusional parasitosis. In the DSM-IV, this corresponds with "delusional disorder, somatic type".

Secondary functional[edit]

Secondary functional delusional parasitosis occurs when the delusions are associated with a psychiatric condition such as schizophrenia or clinical depression.

Secondary organic[edit]

Secondary organic delusional parasitosis occurs when the state of the patient is caused by a medical illness or substance (medical or recreational) use. In the DSM-IV this corresponds with "psychotic disorder due to general medical condition". Physical illnesses that can underlie secondary organic delusional parasitosis include: hypothyroidism, cancer, cerebrovascular disease, tuberculosis, neurological disorders, vitamin B12 deficiency, and diabetes mellitus. Any illness or medication for which formication is a symptom or side effect can become a trigger or underlying cause of delusional parasitosis.

Other physiological factors which can cause formication and thus can sometimes lead to this condition include: menopause (i.e. hormone withdrawal); allergies, and drug abuse, including but not limited to cocaine and methamphetamine (as in amphetamine psychosis).[12] It appears that many of these physiological factors, as well as environmental factors such as airborne irritants, are capable of inducing a "crawling" sensation in otherwise healthy individuals; however, some people become fixated on the sensation and its possible meaning, and this fixation may then develop into delusional parasitosis.[12]


Treatment of secondary forms of delusional parasitosis are addressed by treating the primary associated psychological or physical condition. The primary form is treated much as other delusional disorders and schizophrenia. In the past, pimozide was the drug of choice when selecting from the typical antipsychotics. Currently, atypical antipsychotics such as olanzapine or risperidone are used as first line treatment.

However, it is also characteristic that sufferers will reject the diagnosis of delusional parasitosis by medical professionals, and very few are willing to be treated, despite demonstrable efficacy of treatment.[4]

Popular culture[edit]

The film Hellraiser II has a scene with a mental patient with this condition, who is "prescribed" a straight razor to "remedy" his condition.

In season 3 episode 12 of the television show The X-Files, Scully mentions this condition in conversation with Mulder.

In season 5 episode 7 of the television show House, Dr. Wilson diagnoses Dr. House as having delusional parasitosis.

The animated series The Simpsons makes reference to delusional parasitosis in the motto of the Springfield Psychiatric Center: "Because There May Not Be Bugs On You".

The Philip K. Dick novel A Scanner Darkly contains a character named Jerry Fabin who suffers from intense delusional parasitosis. This detail forms the partly humorous plot of the opening segment of the film adaptation of the story.

The play Bug and subsequent film adaptation are about a couple who experience delusional parasitosis together.

In Scott Sigler's novels Infected and Contagious, skin infestations by alien parasites are discounted as delusional parasitosis, specifically Morgellons.

In the first issue of the comic book Hellblazer, John Constantine's friend believes he is experiencing delusional parasitosis as a result of being a junkie. (As it turns out, he really is covered in insects.)

In Neil Gaiman's The Sandman, Delirium inflicts a curse on a policeman, giving him delusional parasitosis.

In the Dark Skies episode “The Last Wave,” two characters hallucinate insects under their skin as a result of actually having alien bacteria in their bodies.

The sound novel Higurashi no Naku Koro Ni features a character who experienced delusional parasitosis and was driven to self-mutilation, believing maggots were mixed in with her blood and would try to crawl back inside her through the open wounds.

In the Korean film Oldboy, the protagonist is seen hallucinating about ants crawling on his skin as a result of psychosis brought on by his solitary confinement.

In the fantasy roleplaying game Dungeons and Dragons, characters who come into contact with a type of demon called an 'Ekolid' develop this delusion.

In season 10, episode 4 ("The Itch") of the television show Criminal Minds (2014), the unsub has delusional parasitosis, and kills his victims when they don't support his delusion.

DiagnoseMe: season 1, episode 8 (Covered in Bugs), follows a patient suffering skin bugs sensation...formication...due to old amalgam dental fillings [1]

The death metal band Delusional Parasitosis gets their name from the condition.


Main article: Morgellons

The term "Morgellons" was introduced by Mary Leitao in 2004 to describe a skin condition characterized by a range of cutaneous (skin) symptoms including crawling, biting, and stinging sensations; finding fibers on or under the skin; and persistent skin lesions (e.g., rashes or sores). A majority of health professionals, including most dermatologists, regard Morgellons as a manifestation of other known medical conditions, including delusional parasitosis[16][17][18] and have documented that fibers found are from textiles such as clothing.[19] Large-scale studies into the proposed diagnosis by the Centers for Disease Control and Prevention (CDC)[20][21] and the Mayo Clinic[10][11][22] failed to find an infectious cause of the symptoms and confirmed that Morgellons is a variant of delusional parasitosis.

See also[edit]


  1. ^ Freudenmann, R. W.; Lepping, P. (2009). "Delusional Infestation". Clinical Microbiology Reviews. 22 (4): 690–732. doi:10.1128/CMR.00018-09. PMC 2772366free to read. PMID 19822895. 
  2. ^ Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0. 
  3. ^ a b c d Hinkle, N.C. (2011). "Ekbom Syndrome: a delusional condition of "bugs in the skin"". Curr Psychiatry Rep. 13 (3): 178–86. doi:10.1007/s11920-011-0188-0. PMID 21344286. 
  4. ^ a b c d Webb, J.P., Jr. (1993). "Case histories of individuals with delusions of parasitosis in southern California and a proposed protocol for initiating effective medical assistance". Bulletin of the Society of Vector Ecologists. 18 (1): 16–24. 
  5. ^ Kligman, Albert M (2011). "Demodex folliculorum: Requirements for Understanding Its Role in Human Skin Disease". Journal of Investigative Dermatology. 131 (1): 8–10. doi:10.1038/jid.2010.335. PMID 21157421. 
  6. ^ Jing, X., Shuling, G. and Ying, L. (2005). "Environmental scanning electron microscopy observation of the ultrastructure of Demodex.". Microsc. Res. Tech. 68: 284–289. doi:10.1002/jemt.20253. 
  7. ^ Ekbom's syndrome II at Who Named It?
  8. ^ Amin, Omar (February 15, 2015). "The delusion of "delusional parasitosis"" (PDF). Parasite Testing. 
  9. ^ Koblenzer, C.S. (1993). "The clinical presentation, diagnosis and treatment of delusions of parasitosis--a dermatologic perspective". Bulletin of the Society of Vector Ecologists. 18 (1): 6–10. 
  10. ^ a b Hylwa SA, Bury JE, Davis MD, Pittelkow M, Bostwick JM (2011). "Delusional infestation, including delusions of parasitosis: results of histologic examination of skin biopsy and patient-provided skin specimens". Arch Dermatol. 147 (9): 1041–5. doi:10.1001/archdermatol.2011.114. PMID 21576554. 
  11. ^ a b Walsh, Nancy; Zalman S. Agus (May 16, 2011). "Bugs and Worms in Patients' Heads, Not the Skin". MedPage Today. Retrieved 16 May 2011. 
  12. ^ a b c Hinkle, Nancy C (2000). "Delusory Parasitosis" (PDF). American Entomologist. 46 (1): 17–25. 
  13. ^ Grace, Kenneth J (1987). "Delusory Cleptoparasitosis: Delusions of Arthropod Infestation in the Home". Pan-Pacific Entomologist. 63 (1): 1–4. 
  14. ^ Freinhar, Jack P (1984). "Delusions of parasitosis". Psychosomatics. 25 (1): 47–53. doi:10.1016/S0033-3182(84)73096-9. 
  15. ^ FreedBerg; et al. (2003). Fitzpatrick's Dermatology in General Medicine (6th ed.). McGraw-Hill. p. 389. ISBN 0-07-138076-0. 
  16. ^ Mysterious 'Morgellons disease' prompts US investigation, Emma Marris, Nature Medicine, 30 August 2006
  17. ^ Delusions of Parasitosis Noah Scheinfeld, May 4, 2007
  18. ^ Dunn, Jeffrey; Michael B. Murphy; Katherine M. Fox (August 2007). "Diffuse Pruritic Lesions in a 37-Year-Old Man After Sleeping in an Abandoned Building". The American Journal of Psychiatry. 164 (8): 1166–1172. doi:10.1176/appi.ajp.2007.07030381. PMID 17671278. Retrieved 2007-08-04. 
  19. ^ Elaine Monaghan (May 19, 2006). "All in the head?". London: The Times. Retrieved 2007-08-14. 
  20. ^ Pearson, Michele L.; et al. (January 2012). Egles, Christophe, ed. "Clinical, Epidemiologic, Histopathologic and Molecular Features of an Unexplained Dermopathy". PLoS One. 7 (1): e29908. doi:10.1371/journal.pone.0029908. PMC 3266263free to read. PMID 22295070. Retrieved 2012-01-25. 
  21. ^ Aleccia, JoNel. "Mystery skin disease Morgellons has no clear cause, CDC study says". Retrieved 26 January 2012. 
  22. ^ Harding, Anne (May 16, 2011). "Skin infestation a delusion, study says –". CNN. Retrieved 16 May 2011. 

Further reading[edit]

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