Delusional parasitosis

Delusional parasitosis
Delusional parasitosis
Classification and external resources
ICD-9 300.29
DiseasesDB 9622
eMedicine derm/939

Delusional parasitosis (also known as "Ekbom syndrome,"[1] and delusions of parasitosis[2]:60) is a form of psychosis whose victims acquire a strong delusional belief that they are infested with parasites, whereas in reality no such parasites are present.[3] Very often the imaginary parasites are reported as being "bugs" or insects crawling on or under the skin; in these cases the experience of the sensation known as formication may provide the basis for this belief.

Delusional parasitosis is also sometimes referred to as "Ekbom's syndrome", named after a Swedish neurologist, Karl Axel Ekbom,[4] who published seminal accounts of the disease in 1937 and 1938. But this name can be confusing because others use the term Ekbom's syndrome interchangeably with Wittmaack-Ekbom syndrome, another name for restless legs syndrome (RLS). Although delusional parasitosis and RLS were both researched by Ekbom, and RLS sufferers sometimes describe some of their symptoms as if they have, for example, "ants in my veins", the similarities stop there. RLS is a physical condition with physical causes, whereas delusional parasitosis is a false belief.

The false belief of delusional parasitosis stands in contrast to actual cases of parasitosis, such as scabies.

People with delusional parasitosis are likely to ask for help not from psychiatrists but from dermatologists, veterinarians, pest control specialists, or entomologists. Because delusional parasitosis is not at all well known to non-specialists, under those circumstances the condition often goes undiagnosed, or may be incorrectly diagnosed.



Delusional parasitosis is divided into primary, secondary functional and secondary organic groups.[5]


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",[6]:389 and sometimes as "true" delusional parasitosis. In the DSM-IV, this corresponds with "delusional disorder, somatic type".

Secondary functional

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

Secondary organic

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).[7] 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.[7]


Details of delusional parasitosis vary among sufferers, but 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).[3] 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.[8]

Nearly any marking upon the skin, or small object or particle found on the person or their 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.[3] This presenting of "evidence" is known as "the matchbox sign" because the "evidence" is frequently presented in a small container, such as a matchbox.

Delusional parasitosis is seen more commonly in women, and the frequency is much higher past the age of 40.[7]

The peer reviewed Dermatology Online Journal has recently noted a very rare form of delusional parasitosis called delusional tinea.[9]


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.[3]

Delusory cleptoparasitosis

Delusory cleptoparasitosis is a form of delusion of parasitosis where the sufferer believes the infestation is in their dwelling, rather than on or in their body.[10]


The term "Morgellons" was introduced[by whom?] 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[11][12][13] and believe any fibers found are from textiles such as clothing.[14] The Morgellons Research Foundation, a non-profit advocacy organization, believes that it is a new infectious disease that will be confirmed by future research.[15][16] "Other health professionals don't acknowledge Morgellons disease or are reserving judgment until more is known about the condition."[17] Research into the proposed condition is ongoing.

In Popular Culture

In season 5 episode 7 of the television show House Dr.Wilson diagnoses Dr.House as having Delusional Parasitosis.

The Philip K. Dick novel A Scanner Darkly contains a character named Jerry Fabin who suffers from intense Delusional Parasitosis.

The movie Bug (2006 film) is 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.

See also


  1. ^ Rapini, Ronald P.; Bolognia, Jean L.; Jorizzo, Joseph L. (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. ISBN 1-4160-2999-0. 
  2. ^ James, William D.; Berger, Timothy G. (2006). Andrews' Diseases of the Skin: Clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0. 
  3. ^ 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. 
  4. ^ Ekbom's syndrome II at Who Named It?
  5. ^ Freinhar, Jack P (1984). "Delusions of parasitosis". Psychosomatics 25 (1): 47–53. 
  6. ^ Freedberg, et al. (2003). Fitzpatrick's Dermatology in General Medicine. (6th ed.). McGraw-Hill. ISBN 0071380760.
  7. ^ a b c Hinkle, Nancy C (2000). "Delusory Parasitosis" (PDF). American Entomologist 46 (1): 17–25. 
  8. ^ 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. 
  9. ^
  10. ^ Grace, Kenneth J (1987). "Delusory Cleptoparasitosis: Delusions of Arthropod Infestation in the Home" (PDF). Pan-Pacific Entomologist 63 (1): 1–4. 
  11. ^ Mysterious 'Morgellons disease' prompts US investigation, Emma Marris, Nature Medicine, 30 August 2006
  12. ^ Delusions of Parasitosis Noah Scheinfeld, May 4, 2007
  13. ^ Dunn, Jeffrey; Michael B. Murphy and 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. 
  14. ^ Elaine Monaghan (May 19, 2006). "All in the head?". London: The Times. Retrieved 2007-08-14. 
  15. ^
  16. ^ Savely VR, Leitao MM, Stricker RB (2006). "The mystery of Morgellons disease: infection or delusion?". Am J Clin Dermatol 7 (1): 1–5. PMID 16489838. 
  17. ^ "Morgellons disease: Managing a mysterious skin condition". Mayo Clinic. 2007-05-02. Retrieved 2007-08-04. 

Further reading

  • Berrios, G E (1985). Delusional Parasitosis and Physical Disease. Comprehensive Psychiatry 26(5):395-403.
  • Frances, A and Munro, A (1989). Treating a woman who believes she has bugs under her skin. Hospital and Community Psychiatry 40(11):1113-1114.
  • Goddard J (1995). "Analysis of 11 cases of delusions of parasitosis reported to the Mississippi Department of Health". Southern Medical Journal 88 (8): 837–839. 
  • Gould WM, Gragg TM (1976). "Delusions of parasitosis". Archives of Dermatology 112: 1745–1748. 
  • Morris M (1991). "Delusional Manifestation". The British Journal of Psychiatry 159: 83–87. 
  • Rasmussen JE (1990). "Psychosomatic Dermatology". Archives of Dermatology 126: 90–93. 
  • Schrut AH, Waldron WG (1963). "Psychiatric and entomological aspects of delusory parasitosis". JAMA 186 (4): 429–430. 

External links

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