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How to Manage Pests

Pests of Homes, Structures, People, and Pets

Delusory Parasitosis:
What's Attacking Me?

Revised 12/11

In this Guideline:

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The sensation feels like bugs, worms, or mites that are biting, crawling over, or burrowing into, under, or out of your skin. They must be there, because you can feel them, and you are even pretty sure that you can see them. You may also believe that your home or furniture is infested, but you may be the only one who knows they are there. No one seems to think they exist except you. Nothing seems to get rid of them. So what are they—mites, lice, or worms?

And what if your condition seems to be spreading to other family members or to your friends? What if, after trying every reasonable approach and helpful hint from friends, your problem persists? Then it’s time to read the rest of this publication and seek the proper type of professional help.

The first person to contact should be your family physician or primary health care provider. Medical professionals are the only individuals who are licensed to diagnose your condition and recommend specific treatments. Dermatologists, in particular, are trained to deal most effectively with disorders of the skin and their causes, including parasites. If a parasite is causing the disorder, most physicians or their technicians can recognize the most common parasites.

If necessary, the physician can submit medical specimens to entomologists, parasitologists, or other biologists for verification or identification. These narrowly focused experts not only can identify or rule out various kinds of parasites that may be causing your condition, they can provide additional biological information that may greatly assist your physician and you in arriving at a satisfactory diagnosis and treatment. Most entomologists are skilled in identifying various life stages of insects or mites and can use the correct references to determine what they are. Medical entomologists, in particular, spend their careers working with insects, mites, and ticks that attack people. Parasitologists study these and other groups of organisms such as parasitic worms, protozoans, and other invertebrates that live at the expense of their animal hosts.

Initially, you may have tried to solve the problem by consulting nonmedical professionals. However, if you don’t seek professional medical advice, you may miss the opportunity to be properly diagnosed, especially if arthropods or other parasites aren’t the culprits. If you have consulted with any, or perhaps several, of the above mentioned professionals and still no one can pinpoint an offending organism, it’s very unlikely that all of them are wrong. It’s time to reassess your situation and look for a cause other than a pest organism.

Itching, crawling, or burrowing sensations may be the result of many unrelated medical conditions, including:

  • Stress;
  • Reactions to use or abuse of prescription or illicit drugs, particularly methamphetamines;
  • Allergic sensitivity to nonliving substances in your environment (e.g., office paper dust is a well-known example);
  • Dry skin;
  • Mechanical irritants, such as fiberglass filaments;
  • Skin cancers;
  • Vitamin, protein, or other deficiencies in your diet;
  • Diabetes mellitus;
  • Cerebrovascular disease;
  • Hypothyroidism; or
  • Delusory parasitosis.

Thorough testing, including a complete physical checkup by a perceptive physician, should lead to an accurate diagnosis and treatment for most sensations of infestation caused by metabolic disorders or other medical problems listed above. If samples are required, they should be taken directly by the physician and submitted to the experts, if necessary. If a physical and/or thorough allergy and medical testing leave you with a clean bill of health but the symptoms still persist, you have to seriously consider the possibility you may be mistaken in your belief that you are infested with some sort of arthropod or other parasite.

The medical disorder in which a patient has a mistaken belief of being infested by parasites such as mites, lice, fleas, spiders, worms, bacteria, or other organisms is called delusory parasitosis. This belief is based on the sensations felt in the skin that are very real to the sufferer. These sensations of irritation or itching or of crawling organisms are so real the victim is driven to believe that something has to be there. Usually, the patient scratches the itches, but they don’t go away. More scratching leads to rashes, open wounds and sores, and possible infections. Failure to obtain relief from over-the-counter or prescribed medications often drives the sufferer to apply unconventional and sometimes highly toxic compounds to the body in a desperate attempt to alleviate symptoms. Skin conditions can worsen or become much more complicated.

In some cases the parasites appear to be visible to the afflicted person, but they can’t be caught. In a desperate attempt to discover the causative agent, some people will submit pieces of their own tissue to medical or other professionals in an attempt to produce samples of the pests. Such wounds can become serious medical problems.

Very often a corollary problem associated with or causing delusory parasitosis is stress. Stress often manifests itself in people as a nervous habit or “nervous tic,” but those conditions usually aren’t overwhelming. Delusory parasitosis, however, can become debilitating because it tends to amplify the stress level; in turn, the condition worsens.

Stress is known to be associated with many health problems in Americans. Stress may result from numerous experiences including job-related pressures, personal relationships, divorce, loneliness, financial problems, and loss of friends, relatives, or pets. Frequently, reducing or learning to deal with stress coincides with a rapid reduction or elimination of delusory parasitosis.

Your doctor usually can assist in finding ways to reduce your level of stress. However, when delusory parasitosis is persistent, your physician may want to prescribe medicines that alleviate symptoms, at least temporarily, while more permanent solutions are sought. If your physician determines that further therapy or advice is needed, then you may be referred to a psychiatrist. Psychiatrists may prescribe compounds that can successfully treat this disorder. Delusory parasitosis is real, and with professional help it can be medically managed or eliminated altogether.

More information on delusory parasitosis may be obtained from professionals working in county health services offices or University of California Cooperative Extension offices; from county agricultural commissioners; or from the Bohart Museum of Entomology, University of California, Davis Web site delusion.ucdavis.edu.



Berrios, G. E. 1985. Delusional parasitosis and physical disease. Comprehensive Psychiatry 26:395–403.

Damiani, J. T., F. P. Flowers, and D. K. Pierce. 1990. Pimozide in delusions of parasitosis. J. Amer. Acad. Dermatol. 22(2):312–313.

Grace, J. K., and D. L. Wood. 1987. Delusory cleptoparasitosis: delusions of arthropod infestations in the home. Pan-Pacific Entomol. 63(1):1–4.

Koblenzer, C. S. 1993. The clinical presentation, diagnosis and treatment of delusions of parasitosis—a dermatologic perspective. Bull. Soc. Vector Ecol. 18(1):6–10.

Lyell, A. 1985. Delusions of parasitosis. In M. Orkin and H. I. Maibach, eds. Cutaneous Infestations and Insect Bites. New York: Marcel Decker, Inc. pp. 131–137.

Macaskill, N. D. 1987. Delusion parasitosis: successful nonpharmacological treatment of folie-a-deux. Brit. J. Psychiatry 150:261–263.

Marshall, M. A., R. F. Dolezal, M. Cohen, and S. F. Marshall. 1991. Chronic wounds and delusions of parasitosis in the drug abuser. Plast. Reconstr. Surg. 88(2):328–330.

Musalek, M., M. Bach, K. Gerstberger, O. M. Lesch, V. Passweg, J. Wacata, and H. Walter. 1989. Drug therapy of delusional parasitosis. The importance of differential diagnosis for psychophar­macologic treatment of patients with delusional parasitosis. Wiener Medizinische Wochenschrift 139(13):297–302.

Musalek, M., and E. Kutzer. 1990. The frequency of shared delusions in delusions of infestation. European Archives of Psychiatry and Neurological Sciences 239(4):263–266.

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. Bull. Soc. Vector Ecol. 18(1):16–25.


[UC Peer Reviewed]

Pest Notes: Delusory Parasitosis: What's Attacking Me?
UC ANR Publication 7443         PDF to Print

Authors: R. B. Kimsey, Entomology, UC Davis; and E. C. Mussen, Entomology, UC Davis

Produced by UC Statewide IPM Program, University of California, Davis, CA 95616

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