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HE CALLER SAYS THAT SHE IS BEING ATTACKED by invisible mites. The attack has been going on for Tmonths and she has visited a half dozen physicians, but none was able to help her. Two prescribed Kwell lotion (see Glossary), but the sensations persist. She has treated her skin with alcohol, vinegar, Lysol, bleach, kerosene, and various home remedies. She has boiled her bed linens and clothing daily. She can describe the life cycle of the pest and has been able to extract specimens from some of the wounds. She offers to send you samples. She says the irritation is driving her crazy and you are her last hope. How do you respond? At some time nearly everyone experiences a sensation of something burrowing in, crawling on, or pricking the skin (Potter 1992). These tactile perceptions may be caused by a variety of causes, because different stimuli evoke the same limited range of neurocutaneous responses. The conviction that insects are crawling on, biting, or burrowing in the skin, when no arthropod is involved, is termed “delusory parasitosis.” The medical profession defines “delusion” as referring to “a fixed belief” unswayed by evidence to the contrary. By comparison, the term “illusion” refers to situations in which the individual perceives stimuli as produced by arthropods but acknowledges other explanations once they are demonstrated. Although there are some problems with terminology, delusory parasitosis is the phrase used most commonly in the literature, so will be perpetuated here. These cases typically are bewildering to pest control operators, professional entomologists, and medical professionals, who shuffle these sufferers back and forth. Physicians examining the patient determine that the lesions were produced by an insect and recommend calling a pest control company to have the patient's house treated. Conscientious pest control operators perform an inspection and are unable to locate a pest, so refuse to make an insecticide application (St. Aubin 1981). AMERICAN ENTOMOLOGIST • Volume 46, Number 1 Table 1. Common attributes of DP sufferersa
mailed samples to parasitologists for examination. (E) She provided extensive descriptions of the A. Most common in older people (Lyell 1983, Webb 1993, Trabert 1995, Goddard 1995, White 1997) mites and their behavior. (H) She visited B. Disproportionately female (St. Aubin 1981, Lyell 1983, Webb 1993, Trabert 1995) numerous physicians, including a dermatologist, an oculist, a neurologist, as well as the family (1) quitting their jobs (Monk and Rao 1994, Goddard 1995 ) physician; “little help . was forthcoming from (2) burn/destroy furniture (St. Aubin 1981, Lyell 1983, Gieler and Knoll 1990, Goddard 1995) (3) abandon homes (Waldron 1962, Lyell 1983, Driscoll et al. 1993, Goddard 1995) this source.” (I) Duration of the infestation was 17 (4) obsessive laundering/dry cleaning (St. Aubin 1981, Lyell 1983) boil clothing and bed linens years at time of publication. (J) Sensations were described as “itching,” “crawling, scratching and (5) use pesticides dangerously/repeatedly (Lyell 1983, Goddard 1995, White 1997); repeated biting.” (K) She was referred for psychological applications of insecticides to body (Monk and Rao 1994); have used Kwell, Elimite® evaluation; “the patient, however, succeeded in convincing the neurologist that she had no need (6) use home remedies (St. Aubin 1981, Lynch 1993): of his services,” and she published a 25 page a. gasoline (St. Aubin 1981, Koblenzer 1993, Monk and Rao 1994) b. kerosene (St. Aubin 1981, Lynch 1993) treatise to prove that she was not crazy. (L) “To c. other solvents (St. Aubin 1981, Lynch 1993) date, no treatment employed against the mite has d. harsh cleaning compounds (St. Aubin 1981, Lyell 1983) been completely effective.” (M) The delusion also (7) mutilate body attempting to remove offending vermin (St. Aubin 1981, Lyell 1983, Zanol et Traver’s (1951) article provides notable docu- D. Provide skin scrapings, bits of debris (in paper, small jars) (Pomerantz 1959, Waldron 1962, Lyell mentation of the effort expended extracting and 1983, Goddard 1995) “One characteristic sign in delusory parasitosis is the complainant's “identifying” specimens. In addition to the above eagerness to provide samples of their alleged parasites in small containers” (May and Terpenning 1991). Samples provided in adhesive tape, plastic bags, or vacuum bags (Webb 1993, Koblenzer characteristics common to delusory parasitosis 1993, White 1997) “there are millions of them”-yet specimen cannot be obtained sufferers, Traver described the pests as primarily E. Can provide extensive, elaborate, involved descriptions of the pests, their life cycle, and behaviors active at night and identified animals as the likely (Lynch 1993, Monk and Rao 1994, Zanol et al. 1998) infestation source, other commonalities (Hinkle F. Social isolation (Koblenzer 1993, Trabert 1995), self-employed (Lyell 1983), abandon family to 1998). Reflecting the often cited bias of delusory avoid infesting them (Lynch 1993, Monk and Rao 1994) parasitosis cases toward women (Trabert 1995, G. Emotional trauma such as job loss, divorce/separation (Lyell 1983, Grace and Wood 1987, Webb White 1997), 22 (65%) of the past 34 delusory H. Have seen numerous physicians, all to no avail (Driscoll et al. 1993, Lyell 1983) parasitosis cases I have had were female and 12 I. Mean duration of delusion was 3.0 ± 4.6 years (median, I year) (Trabert 1995); “Years of (35%) were male. Of these, three pairs involved suffering” (Pomerantz 1959, Driscoll et al. 1993), 12-year history (Monk and Rao 1994), 40 years folie a deux, the phenomenon occurring in up to one-third of cases (Koblenzer 1993), in which J. Complain of “itching, crawling, pinprick biting sensations” (White 1997), “formication” (Koo and close associates experience the same delusion. Although the prevalence of delusory parasitosis K. Reject possibility of psychological or other explanations (Trabert 1995) “I'm not crazy.” “I am not imagining this.” Vehemence indicative of DP (Zanol et al. 1998). “ Exceptional strength of may be considered low by the medical profession conviction regarding infestation” (Lynch 1993) almost diagnostic for DP (Webb 1993) (Driscoll et al. 1993), the pest control industry and L. Express desperation, “you are my last hope” (Nutting and Beerman 1983, Lynch 1993) medical entomologists encounter it all too M. Delusion eventually shared by another family member (St. Aubin 1981) in up to 1/3 of cases frequently (Schrut and Waldron 1963, Kushon et Citations are illustrative of some of the published descriptions. Glossary
Description of Delusory Parasitosis
Delusion: a false belief that persists despite the
Descriptions of delusory parasitosis sufferers are remarkably consistent (Koblenzer 1993) with Dermatitis: inflammation of the skin.
common attributes (Table 1). The most common Elimite: a permethrin cream used to treat for
symptoms include paresthesia, pruritus, (see Glossary), and a biting sensation (Hinkle 1998).
Erythema: abnormal redness of the skin.
The classic delusory parasitosis case remains Formication: the sensation of ants crawling on
that of J. R. Traver (1951), a zoologist who Idiopathic: of unknown cause.
published her personal account of 17 years of Illusion: misinterpretation of perception of
dealing with an "infestation" in her own body; the following descriptions correspond to common Kwell: prescription lindane formulations used in
delusory parasitosis attributes listed in Table 1. According to Poorbaugh (1993), (A) she was 40 years old at onset of symptoms and suffered with Paresthesia: a sensation of pricking, tingling, or
them for another 40 years until her death at age 80. (B) She was female. (C) She used pesticides Pruritus: itching.
both dangerously and repeatedly, applied home Scarification: wound or cut marks from
remedies to her body, and mutilated her body by "digging out" mites with fingernails. (D) She Urticaria: stinging or burning itch.
collected material from her scalp and body and AMERICAN ENTOMOLOGIST • Spring 2000
al. 1993). Of the 21 cooperative extension Table 2. DP sufferers’ descriptions of what is infesting them
specialists providing estimates of their delusory parasitosis cases, the average number was 17 per 1. Black and white, but change colors (Waldron 1962, St. Aubin 1981, Monk and Rao 1994) year (range, 4-45), occupying 2.4% of these 2. Jump or fly (Waldron 1962, Monk and Rao 1994) specialists’ time (Hinkle 1998). 3. Have eight little legs and a small sucker (Gieler and Knoll 1990) Many delusory parasitosis sufferers who come 4. Half moon shape, like the end of a fingernail (Lyell 1983, Hinkle 1998) to entomologists already have received a 5. Moth-like creatures (Monk and Rao 1994, Hinkle 1998) 6. Waxy looking fuzz balls (Schrut and Waldron 1963, Hinkle 1998) prescription for Kwell (lindane) from a physician, 7. Granules about the size of a grain of salt (Schrut and Waldron 1963, de Leon et al. 1992, Hinkle implying that scabies had been diagnosed. However, scabies is the default diagnosis for any 8. Long hairs that move independently (Hinkle 1998) idiopathic dermatitis or pruritus (Pariser and Pariser 9. Tiny white worm with a brown bulb on its head (Hinkle 1998) 1987). Frequently, the placebo effect of such 10. Worm-like coating around the hair root, with a black bulb attached (Hinkle 1998) medications will effect temporary remission of the 11. Greenish-grey cigar shaped things (Hinkle 1998) 12. Infest inanimate objects: automobiles, furniture, clothing, rugs (Grace and Wood 1987) symptoms, but they almost invariably recur (St. Aubin 1981). Typically, the cause is not any insect or other Some contactants producing paresthesia are arthropod but, instead, is some physical (Blum and discussed by Fisher (1995) and include solvents, Katz 1990, Potter 1992), physiological, or fabrics, and fabric finishes. Two particularly unusual psychological stimulus. Victims attempt to correlate situations are when exposure to either water what they see, or think they see, with their physical (aquagenic pruritus) or air (atmokinesis) produces perceptions. Thus, sufferers intently examine the pruritus or paresthesia in susceptible individuals area experiencing the sensation, digging out (Bernhard 1989, Bircher 1990). blackheads, hair follicles, and other normal skin Demonstration of scarification is indicative only components to account for the sensation (Lynch of scratching; it proves nothing about the stimulus 1993). Descriptions by some delusory parasitosis causing the scratching (Fig. 1). Self-excoriation is a sufferers of their pests are listed in Table 2. common feature of delusory parasitosis, despite the individuals’ protestations that they do not scratch Physical Causes
Physical causes include any external stimulus Scratching may produce papular eruptions. Any that yields a sensation of paresthesia, pruritus, repeated skin irritation produces a friction blister. urticaria, or similar irritation. Blum and Katz (1990) Repeated rubbing of an area often produces a bleb summarized potential physical causes that could be (small blister) which, when ruptured, yields an open attributed to delusory parasitosis symptoms. These sore that may become infected. Once the sore included static electricity, chemicals such as some begins oozing plasma and a scab forms, hairs and pyrethroid insecticides, or mechanical irritants such cloth fibers become entrapped in the sticky fluid. as fiberglass filaments and paper shards. Volatile These flecks are dislodged and called mites or chemicals from manufactured building materials insects because they look like they have “antennae” such as paneling and carpeting can produce itching and “legs” (Fig. 2). Hair follicles often are pulled and stinging sensations (Jaakkola et al. 1994). There out; the follicle accompanied by the associated are many non-arthropod agents capable of sebaceous gland looks like a worm. producing delusory parasitosis symptoms; under these circumstances an industrial hygienist can survey and make recommendations (Potter 1992). Dry, sensitive skin is particularly susceptible to these sensations. Particles impinging on the skin as a result of static electricity may be perceived as “bites” or “stings.” This is particularly true of materials with sharp projections such as paper, metal, and fiberglass fragments. Carpet fibers also may be attracted to lower portions of the body because of static electricity, and these too can feel like pinpricks. Electronic equipment generates an electrostatic charge, so office equipment and computer components can produce sufficient attraction to various materials to be irritating to susceptible individuals. Most persons experiencing itching will rub or scratch briefly and absentmindedly without consciously noticing the sensation. Others, however, focus on the itch until it occupies all of their attention. Thus, delusory parasitosis sufferers Fig. 1. Scarification indicates scratching but
Fig. 2. A scab with entrapped hairs and
become fixated on the perceived irritation. fibers is said to look like a “bug.” AMERICAN ENTOMOLOGIST • Volume 46, Number 1
Table 3. Some medical conditions producing delusatory parasitosis symptoms
of many infectious and noninfectious diseases, as well as numerous other medical conditions (Blum and Katz 1990). Those listed in Table 3 are not to be taken as explanations for all delusory parasitosis cases, merely as an indication of the range of medical conditions with manifestations that reflect Age-related neurological degenerative changes can produce phantom limblike sensations, including pruritus and urticaria, in some elderly patients X (Bernhard 1992). This phenomenon may explain the disproportionate number of delusory parasitosis Allergies are one common cause of pruritus, hemochromatosisa X - X - - hepatic diseasea X - X - X erythema, and urticaria. Food and skin allergies may produce these symptoms. Some common food allergies include those to milk, egg white, soybean, peanut, chocolate, wheat, food additives, mangoes, oranges, nuts, and pineapple (Kabir et al. 1993, X McGowan and Gibney 1993, Levy et al. 1994). Atopic dermatitis can be caused by skin allergies to such materials as latex, textiles, soap, detergent, fabric softeners, shampoo, lotions, insect repellents, deodorants, and any other substance that contacts the skin (Simion et al. 1995). Most contain fragrances, colorants, stabilizers, emulsifiers, preservatives, and other components that may sensitize susceptible individuals (Phillips 1992). Numerous medical conditions have itching or other skin irritations as symptoms, emphasizing the importance of not dismissing such symptoms as “just delusory parasitosis.” Prodromal sensations should be investigated medically as indicators of potentially life-threatening conditions (Pariser and j Lyell 1983. k Scherbenske et al. 1989. Pariser 1987). Nutritional deficiencies can produce itching as can high doses of many minerals and fat- soluble vitamins (Phillips 1992, Zanol et al. 1998). Some people claim they see the “creatures” Medications. Paresthesia, erythema, urticaria,
jump (Waldron 1962). This is probably caused by pruritus, and hives are listed as potential side effects static electricity or magnetic charges of tiny of most prescription and over-the-counter particles (Ebeling 1978). Some people see dust and medications (Table 4). Incidence of these symptoms other motes floating in a shaft of sunlight and may be increased by interaction of two or more of claim they are tiny flying creatures. Even the these drugs, as is particularly common in the elderly random motion of particles floating on water is (Doucet et al. 1996). Drug-induced delusory parasitosis has been demonstrated definitively in only a few cases (Aizenberg et al. 1991). Physiological Causes
Delusory parasitosis may result from methamphetamine particularly are prone to produce physiological causes such as allergies, nutritional the sensation of insects crawling on or burrowing in deficiencies, drug reactions, and other medical conditions. Allergies can include inhalant allergies, The 50 most commonly prescribed drugs in the ingestant reactions, and contact dermatitis. United States list at least one symptom commonly Nutritional deficiencies or overdoses may produce attributed to delusory parasitosis (Table 4). These both systemic and dermal reactions (Eliason et al. include erythema (56%), paresthesia (56%), pruritus 1997). Drug reactions include responses to single (64%), urticaria (66%), and rash (92%). Although drugs as well as multiple drug interactions. these side effects may be rare, the fact that these Medical Conditions. Medical literature from
data are based on more than 2 billion prescriptions the past 5 years shows more than 100 different indicates that these drugs are being used extensively causes of itching including infection with bacteria, and that an increasing proportion of patients will fungi, viruses, nematodes, and various other experience these ancillary reactions and possibly pathogens and parasites (Phillips 1992). Pruritus, attribute them to unseen “bugs” (Fig. 3). paresthesia, and urticaria are common side effects AMERICAN ENTOMOLOGIST • Spring 2000 Table 4. Fifty most commonly prescribed U.S. drugs and some side effectsa

Brand Name
Generic Name
Drug Type
Erythema
Paresthesia
Pruritus
Urticaria
a Sandow 19998, based on more than two billion 1997 U.S. prescriptions. Drugs disproportionately prescribed for the effects: the elderly take multiple medications elderly such as those for heart conditions, simultaneously (prescription and over-the-counter), glaucoma, osteoporosis, impotence, and arthritis frequently receive prescriptions from more than one particularly may be predisposed to cause these side effects (May and Terpenning 1991). These drugs instructions or forget how often they have include insulin, estrogen, arthritis medications, medicated themselves, and drug pharmacokinetics hypertension drugs, beta blockers, MAO inhibitors, vary by patient age. Persons over 65 years old represent only 12% of the population but receive Several factors contribute to the predisposition more than 30% of all prescription drugs (Jones of elderly people to experience adverse drug 1997). Older adults average three prescription AMERICAN ENTOMOLOGIST • Volume 46, Number 1 medications per day, 15 different prescriptions per (Schino et al. 1996). There are strong socio- year, and consume 70% of all over-the-counter psychological implications of self-grooming, drugs. Approximately 25% of their hospital reflecting group status, individual self-image, and admissions are a result of incorrect prescription drug psychological well-being. Touching, scratching, and usage. One in five Americans over the age of 60 rubbing are viewed as forms of self-assurance, regularly takes pain medication and one in four who consolation, and validation of the psyche (Schino et does so experiences side effects caused by the al. 1991, Troisi et al. 1991). This dynamic is displayed medication; one in ten is hospitalized as a result in meetings, in one-on-one confrontations between (Chrischilles et al. 1992). individuals, and in other human interactions. Herbal remedies and nutritional supplements may produce untoward side effects including pruritus and depression, and tiredness can manifest themselves urticaria (Huxtable 1990, Cetaruk and Aaron 1994). as itching and tingling (Gieler and Knoll 1990, Additionally, they may interfere with or potentiate Gupta et al. 1994, Gupta 1995, Woodruff et al. prescription and over-the-counter medications, 1997). Although it is generally recognized that stress resulting in unanticipated effects. can induce headaches, high blood pressure, acne, Although this is by no means an exhaustive heart attacks, and ulcers, delusory parasitosis review of medication side effects, it does show that sufferers are reluctant to acknowledge that their Fig. 3. Side effects of Prozac®,
symptoms experienced by delusory parasitosis dermatologic symptoms could be related to stress sufferers may have valid physiological causes, either in medical conditions or in the drugs prescribed for Social isolation is one predisposing feature of their treatment. Psychologists and dermatologists delusory parasitosis. Some delusory parasitosis cases have noted that organic causes must be excluded involve lonely people who need interactions with parasitosis—erythema, paresthesia, pruritus, rash, before a diagnosis of psychogenic pruritus can be other humans (May and Terpenning 1991). Elderly made (Freyne and Wrigley 1994, Gupta 1995). people who live alone, seldom get out, seldom have Because of the numerous potential physiological visitors, or feel they have no purpose in life are causes of pruritus, urticaria, and paresthesia, it is prone to fixating on themselves and their health understandable that physicians often do not attempt (Bernhard 1992, Freyne and Wrigley 1994). For to treat underlying causes but, instead, prescribe many of these people, the illness itself is an palliatives or advise the patient to pursue important security factor (Laihinen 1991), allowing entomological possibilities (which fits with the them to seek attention and evoke sympathy. patient's inclinations, anyway). In these days of Bell's Syndrome (the Power of Suggestion). managed care, physicians have neither the time nor Often, the fact that several people are experiencing incentive to do a thorough medical workup or the same sensation is used to demonstrate that it is attempt to determine causation of obscure and non- not psychological. Scratching behavior is an atavistic primate response with high psychological In teenagers and young adults, recreational drug contagiousness (de Leon et al. 1992). Thus, use may be a more likely explanation for delusory situations in which more than one person is parasitosis symptoms (Zanol et al. 1998). Drugs such complaining of the symptoms are not necessarily as cocaine and methamphetamine particularly are evidence that there is a common cause behind the noted for producing “formication,” or the sensation of ants crawling in or on the skin (Ellinwood 1969, Siegel 1978, Elpern 1988, Marschall et al. 1991). parasitosis cases will attest to this. Despite finding Cocaine use is admitted by 19% of all 18-25 year olds no arthropod in any samples provided, there is a and 26% of all 26-34 year olds; hallucinogens such as strong urge to take a shower following these methamphetamines have been used by 12% of 18-25 examinations. Consciously, one realizes that there is year olds and 16% of 26-34 year olds (SAMHSA no infestation, but subconsciously one often feels 1996). Ekbom’s (1938) syndrome caused by drug use the “creepy-crawlies” after looking through the was featured in an episode of “The X Files” (Hinkle victim’s scurf. In fact, the author, while reading 1998), thus assuming its place in popular culture. through the delusory parasitosis literature in preparing this article, found herself absentmindedly Psychological Causes
scratching; before the manuscript was completed, Scratching is a common primate displacement her arms and legs bore distinct scarification. activity in response to tension, anxiety, and stress Responses of the Entomologist or Pest
Table 5. Some web sites dealing with delusory parasitosis
Control Operator
It always should be determined whether, in fact, Cultural entomology http://www.insects.org/ced2/insects_psych.html
an arthropod is involved (Table 5). Monitoring may Factsheet http://www.ianr.unl.edu/ianr/lanco/enviro/pest/factsheets/009-95.htm
include using cellophane tape to entrap the culprit Imaginary infestations http://www.medscape.com/SCP/IIM/1998/vl5.n03/m4174.godd/
m4174.godd.html
while it is attacking the skin, glueboards to survey National Geographic http://www.nationalgeographic.com/media/ngm/9812/fngm/
the environment, or a hand-operated vacuum cleaner to sample the area in which attacks are AMERICAN ENTOMOLOGIST • Spring 2000 occurring (Potter 1992). Typical culprits include recommendations for their suppression (Waldron thrips brought in on flowers, bird or rodent mites 1972). Unfortunately, it typically is impossible to from nests in the building, or cryptic pests such as convince the individual that there are no “bugs” bed bugs or fleas (Webb 1993). If a causative agent present, and recommendations to visit a health care is identified, the source can be eliminated and the professional virtually always are rebuffed (Lynch problem solved. Otherwise, no pesticidal 1993). applications should be made (Potter 1992). Entomologists should have the courage of their Monitoring and careful investigation of the convictions. Once it has been determined that there situation may indicate that, although no arthropod are no arthropods involved in the case, this should is involved, there are physical causes such as be conveyed to the individual tactfully but firmly. insulation being blown through air-handling The letter may be worded to make the point that, systems or nylon fragments from newly installed “Although examination of the specimens you carpet (Blum and Katz 1990, Potter 1992). provided yielded no evidence of arthropod Frequently, such modifications as improved involvement, the symptoms you are experiencing sanitation, installation of antistatic devices, and are real and deserve further investigation.” The increased humidity will reduce complaints. objective is to persuade the sufferer to go to a If no entomological cause can be identified, the physician where, it is hoped, he or she may receive individual should be referred to a physician and appropriate health care (Lynch 1993, Hinkle 1998).
encouraged to pursue the possibility of one of the As Elliott (1944) observed over half a century ago,
previously mentioned medical conditions serving as investigating delusory parasitosis is “an intriguing
the basis of the symptomatology (Kushon et al. field for useful research, an opportunity for
1993). Meanwhile, the sufferer should be advised to teamwork on the part of the pest control operator,
discontinue using self-prescribed treatments. These the medical entomologist, the dermatologist, and
materials, applied topically, are not good for the the psychiatrist.”
skin and may aggravate the problem. In particular,
pesticidal shampoos and lotions should not be used Acknowledgments
more than stated specifically on the label; these are
I thank F. M. Oi, of the USDA-ARS, Center for potent compounds that will increase skin sensitivity Medical, Agricultural & Veterinary Entomology, when overused. Gainesville, Florida, who supplied the persistent Responsible pest control firms have policies encouragement that resulted in this article. Grateful against treating for pests until a culprit has been appreciation goes to the more than 70 Cooperative identified. This is legally and ethically appropriate Extension Specialists around the country who (St. Aubin 1981). Customers, however, frequently participated in our delusory parasitosis survey, as do not understand, expecting that the pest control well as the other contributors who alerted me to operator will “just spray something.” Pressure to valuable literature and sources. I am grateful to the comply may be extreme. By applying pesticides, the on-line discussion group Entomo-l for providing pest control operator is validating the customer’s diverse accounts of and perspectives on delusory perception that there is a pest present. Unwarranted parasitosis. Acknowledgment (without appreciation) pesticidal applications increase the building’s goes to the hundreds of delusory parasitosis pesticide load. Pesticide exposure can increase sufferers who have provided me this experience. symptom manifestations, both as psychological responses and as physiological reactions to the References Cited
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