Delusory-Parasitosis-Nancy-Hinkle

Delusory Parasitosis 

Nancy C. Hinkle 

Trw CALLER SAYS THAT SHE IS BEING ATTACKED by 

invisible mites. The attack has been going on 

for months and she has visited a half dozen 

physicians, but none was able to help her. Two 

prescribed Kwelliotion (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 

arc 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 siruations 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). 

A~IFRICAN ENTOMOLOGIST • VO/llme 46, Number 1 

DRIVING 

ME CRAZY' 

ALAN KAHAN 

17

Table 1. Common attributes of DP sufferers' 

A. Most common in older people (Lyell 1983, Webb 1993, Trabert 1995, Goddard 1995, 

White 1997) 

B. Disproportionately female (St. Aubin 1981, Lyell 1983, Webb 1993, Trabert 1995) 

C. Exhibir behaviors such as: 

(1) quitting their jobs (Monk and Rao 1994, Goddard 1995) 

(2) burn/destroy furniture (St. Aubin 1981, Lyell 1983, Gieler and Knoll 1990, 

Goddard 1995) 

(3) abandon homes (Waldron 1962, Lyell 1983, Driscoll et a!. 1993, Goddard 1995) 

(4) obsessive laundering/dry cleaning (St. Aubin 1981, Lyell 1983) boil clothing and 

bed linens (Ebeling 1978) 

(5) use pesticides dangerouslylrepeatedly (Lyell 1983, Goddard 1995, White 1997); 

repeated applications of insecticides to body (Monk and Rao 1994); have used 

Kwell®, Elimite® (Webb 1993) 

(6) use home remedies (St. Aubin 1981, Lynch 1993): 

a. gasoline (St. Aubin 1981, Koblenzer 1993, Monk and Rao 1994) 

b. kerosene (St. Aubin 1981, Lynch 1993) 

c. other solvents (St. Aubin 1981, Lynch 1993) 

d. harsh cleaning compounds (St. Aubin 1981, Lyell 1983) 

(7) murilate body attempring to remove offending vermin (Sr. Aubin 1981, Lyell 1983, 

Zanol et a!. 1998) 

D. Provide skin scrapings, bits of debris (in paper, small jars) (Pomerantz 1959, Waldron 

1962, Lyell 1983, Goddard 1995) "One characteristic sign in delusory parasirosis is rhe 

complainant's 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 1993, Whire 1997) "there are millions of 

them"-yet specimen cannot be obtained 

E. Can provide extensive, elaborate, involved descriptions of the pests, rheir life cycle, 

and behaviors (Lynch 1993, Monk and Rao 1994, Zanol et a!. 1998) 

F. Social isolation (Koblenzer 1993, Trabert 1995), self-employed (Lyell 1983), abandon 

family to avoid infesting them (Lynch 1993, Monk and Rao 1994) 

G. Emotional trauma such as job loss, divorce/separation (Lyell 1983, Grace and Wood 

1987, Webb 1993, Lynch 1993) 

H. Have seen numerous physicians, all to no avail (Driscoll et a!. 1993, Lyell 1983) 

l. Mean duration of delusion was 3.0 ± 4.6 years (median, 1 year) (Trabert 1995); 

"Years of suffering" (Pomerantz 1959, Driscoll et al. 1993), 12-year history (Monk 

and Rao 1994), 40 years (Poorbaugh 1993) 

J. Complain of "itching, crawling, pinprick biting sensations" (White 1997), "formication" 

(Koo and Gambia 1996) 

K. Reject possibility of psychological or other explanations (Trabert 1995) "I'm not 

crazy." "J am not imagining this."Vehemence indicative of DP (Zanol et a!. 1998). 

"Exceptional strength of conviction regarding infesration" (Lynch 1993) almosr 

diagnostic for DP (Webb 1993) 

L. Express desperation, "you are my last hope" (Nutting and Beerman 1983, Lynch 

1993) 

M. Delusion eventually shared by another family member (St. Aubin 1981) in up to 1/3 of 

cases (Koblenzer 1993) 

'Citations 

18 

arc illustrative of some of the published descriptions. 

Description of Delusory Parasitosis 

Descriptions of delusory parasitosis sufferers 

are remarkably consistent (Koblenzer 1993) with 

common attributes (Table 1). The most common 

symptoms include paresthesia, pruritus, (see Glossary), 

and a biting sensation (Hinkle 1998). 

The classic delusory parasitosis case remains 

that of J. R. Traver (1951), a zoologist who published 

her personal account of 17 years of dealing 

with an "infestation" in her own body; the following 

descriptions correspond to common delusory 

parasitosis attributes listed in Table 1. According 

to Poorbaugh (1993), (A) she was 40 years old at 

onset of symptoms and suffered with them for 

another 40 years until her death at age 80. (B) She 

was female. (C) She used pesticides both danger- 

ously and repeatedly, applied home remedies to her 

body, and murilated her body by "digging out" mites 

with fingernails. (D) She collected material from her 

scalp and body and mailed samples to parasitologists 

for examination. (E) She provided extensive 

descriptions of the mites and their behavior. (H) She 

visited numerous physicians, including a dermatologist, 

an oculist, a neurologist, as well as the family 

physician; "little help ... was forthcoming from this 

source." (I) Duration of the infestation was 17 years 

at time of publication. (J) Sensations were described 

as "itching," "crawling, scratching and biting." (K) 

She was referred for psychological evaluation; "the 

patient, however, succeeded in convincing the neurologist 

that she had no need of his services," and 

she published a 25 page treatise to prove that she 

was not crazy. (L) "To date, no treatment employed 

against the mite has been completely effective." (M) 

The delusion also was shared by two other family 

members. 

Traver's (1951) article provides notable documentation 

of the effort expended extracting and 

"identifying" specimens. In addition to the above 

characteristics common to delusory parasitosis 

sufferers, Traver described the pests as primarily 

active at night and identified animals as the likely 

infestation source, other commonalities (Hinkle 

1998). Reflecting the often cited bias of delusory 

parasitosis cases toward women (Trabert 1995, 

White 1997),22 (65%) of the past 34 delusory 

parasitosis cases I have had were female and 12 

(35%) were male. Of these, three pairs involved 

folie a deux, the phenomenon occurring in up to 

one-third of cases (Koblenzer 1993), in which close 

associates experience the same delusion. 

Although the prevalence of delusory parasitosis 

may be considered low by the medical profession 

(Driscoll et al. 1993), the pest control industry 

and medical entomologists encounter it all too 

frequently (Schrut and Waldron 1963, Kushon et 

GIo8ury 

Delusion: a false belief that persists despite 

the facts. 

Dennatitis: inflammation of the skin. 

Elimite: a permethrin cream used to treat for 

scabies and lice. 

Erythema: abnormal redness of the skin. 

Formication: the sensation of ants crawling 

on the skin. 

Idiopathic: of unknown cause. 

Illusion: misinterpretation of perception of 

something objectively existing. 

KweU:prescription lindane formulations used 

in scabies (cream) and lice(shampoo) treatment. 

Paresthesia: a sensation of pricking, tingling, 

or creeping on the skin. 

Pruritus: itching. 

Scarification: wound or cut marks from 

scratching. 

Urticaria: stinging or burning itch. 

AMERICAN ENTmlOl.OGIST • Spring 2000

al. 1993). Of the 21 cooperative extension specialists 

providing estimates of their delusory parasitosis 

cases, the average number was 17 per year 

(range, 4-45), occupying 2.4% of these specialists' 

time (Hinkle 1998). 

Many delusory parasitosis sufferers who come 

to entomologists already have received a prescription 

for Kwell (lindane) from a physician, implying 

that scabies had been diagnosed. However, scabies 

is the default diagnosis for any idiopathic dermatitis 

or pruritus (Pariser and Pariser 1987). Frequently, 

the placebo effect of such medications will 

effect temporary remission of the symptoms, but 

they almost invariably recur (St. Aubin 1981). 

Typically, the cause is not any insect or other 

arthropod but, instead, is some physical (Blum and 

Katz 1990, Potter 1992), physiological, or psychological 

stimulus. Victims attempt to correlate 

what they see, or think they see, with their physical 

perceptions. Thus, sufferers intently examine the 

area experiencing the sensation, digging out blackheads, 

hair follicles, and other normal skin components 

to account for the sensation (Lynch 1993). 

Descriptions by some delusory parasitosis sufferers 

of their pests are listed in Table 2. 

Physical Causes 

Physical causes include any external stimulus that 

yields a sensation of paresthesia, pruritus, urticaria, 

or similar irritation. Blum and Katz (1990) summarized 

potential physical causes that could be attributed 

to delusory parasitosis symptoms. These included 

static electricity, chemicals such as some pyrethroid 

insecticides, or mechanical irritants such as 

fiberglass filaments and paper shards. Volatile chemicals 

from manufactured building materials such as 

paneling and carpeting can produce itching and stinging 

sensations (Jaakkola et al. 1994). There are many 

non-arthropod agents capable of producing delusory 

parasitosis symptoms; under these circumstances 

an industrial hygienist can survey and make 

recommendations (Porrer 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 become 

fixated on the perceived irritation. 

Some contactants producing paresthesia are 

discussed by Fisher (1995) and include solvents, 

fabrics, and fabric finishes. Two particularly un- 

Table 2. DP sufferers' descriptions of what is infesting them 

1. Black and white, but change colors (Waldron 1962, St. Aubin 1981, Monk and Rao 

1994) 

2. Jump or fly (Waldron 1962, Monk and Rao 1994) 

3. Have eight little legs and a small sucker (Gieler and Knoll 1990) 

4. Half moon shape, like the end of a fingernail (Lyell 1983, Hinkle 1998) 

5. Moth-like creatures (Monk and Rao 1994, Hinkle 1998) 

6. Waxy looking fuzz balls (Schrut and Waldron 1963, Hinkle 1998) 

7. Granules about the size of a grain of salt (Schrut and Waldron 1963, de Leon et al. 

1992, Hinkle 1998) 

8. Long hairs that move independently (Hinkle 1998) 

9. Tiny white worm with a brown bulb on its head (Hinkle 1998) 

10. Worm-like coating around the hair root, with a black bulb attached (Hinkle 1998) 

11. Greenish-grey cigar shaped things (Hinkle 1998) 

12. Infest inanimate objects: automobiles, furniture, clothing, rugs (Grace and Wood 

1987) 

usual situations are when exposure to either water 

(aquagenic pruritus) or air (atmokinesis) produces 

pruritus or paresthesia in susceptible individuals 

(Bernhard 1989, Bircher 1990). 

Demonstration of scarification is indicative only 

of scratching; it proves nothing about the stimulus 

causing the scratching (Fig. 1). Self-excoriation is a 

common feature of delusory parasitosis, despite 

the individuals' protestations that they do not 

scratch (Marschall et al. 1991). 

Scratching may produce papular eruptions. Any 

repeated skin irritation produces a friction blister. 

Repeated rubbing of an area often produces a bleb 

(small blister) which, when ruptured, yields an open 

sore that may become infected. Once the sore begins 

oozing plasma and a scab forms, hairs and 

cloth fibers become emrapped in the sticky fluid. 

These flecks are dislodged and called mites or insects 

because they look like they have "antennae" 

and "legs" (Fig. 2). Hair follicles often are pulled 

out; the follicle accompanied by the associated sebaceous 

gland looks like a worm. 

Fig. 1. Scarification indicates scratching 

but offers no clue as to its cause. 

Fig. 2. A scab with entrapped hairs and 

fibers is said to look like a "bug." 

A~IEI\ICAN ENTOMOLOGIST • Volume 46, Number 1 19

Table 3. Some medical conditions producing delusatory parasitosis symptoms 

Condirion 

Some people claim they see the "creatures" jump 

(Waldron 1962). This is probably caused by static 

electricity or magnetic charges of tiny particles 

(Ebeling 1978). Some people see dust and other 

motes floating in a shaft of sunlight and claim they 

are tiny flying creatures. Even the random motion 

of particles floating on water is perceived as deliberate 

movement. 

Symproms 

urticaria erythema paresrhesia 

AIDS' X X X 

anemia' X X X 

auroimmune disease' X 

carbon monoxide b 

X 

carcinoma" X X X 

cholestasis' X X 

cirrhosis' X X 

depression' X X 

diabetes mellitus' X X X 

fluoride poisoning' 

X 

heavy metal toxicityd X X 

hemochromarosis' X X 

hepatic disease' X X 

hyperthyroidism' X X X 

hypoglycemia' X X 

hypothyroidism' X X 

lupus f 

X 

lymphomas 

X 

menopause h X X 

multiple sclerosis' X X 

neoplasia' 

X 

niacin overdosei X X 

rheumaroid arthritis k X X 

stress' X X 

uremia' X X 

n Phillips 1992. 

b Levit 1995. 

C Arnow et a!. 1994. 

d Kazantzis 1978. 

C Sacerdote 1987. 

f Kapadia and Haroon 1996. 

g Blum and Katz 1990. 

h Pansini et a!. 1994. 

i Ostermann and Westerberg 1975. 

i Lyell 1983. 

k Scherbenske et a!. 1989. 

pruritus 

Physiological Causes 

Delusory parasitosis may result from physiological 

causes such as allergies, nutritional deficiencies, 

drug reactions, and other medical conditions. Allergies 

can include inhalant allergies, ingestant reactions, 

and contact dermatitis. Nutritional deficiencies 

or overdoses may produce both systemic 

and dermal reactions (Eliason et al. 1997). Drug 

reactions include responses to single drugs as well 

as multiple drug interactions. 

Medical Conditions. Medical literature from the 

past 5 years shows more than 100 different causes 

of itching including infection with bacteria, fungi, 

viruses, nematodes, and various other pathogens 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

rash 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

and parasites (Phillips 1992). Pruritus, paresthesia, 

and urticaria are common side effects 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 typical 

delusory parasitosis symptoms. 

Age-related neurological degenerative changes 

can produce phantom limb like sensations, including 

pruritus and urticaria, in some elderly patients 

(Bernhard 1992). This phenomenon may explain 

the disproportionate number of delusory parasitosis 

cases among the elderly (Trabert 1995). 

Allergies are one common cause of pruritus, 

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, 

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 Pariser 1987). Nutritional deficiencies 

can produce itching as can high doses of many 

minerals and fat-soluble vitamins (Phillips 1992, 

Zanol et al. 1998). 

Medications. Paresthesia, erythema, urticaria, 

pruritus, and hives are listed as potential side effects 

of most prescription and over-the-counter 

medications (Table 4). Incidence of these symptoms 

may be increased by interaction of two or more of 

these drugs, as is particularly common in the elderly 

(Doucet et al. 1996). Drug-induced delusory 

parasitosis has been demonstrated definitively in 

only a few cases (Aizenberg et al. 1991). Recreational 

drugs such as cocaine and methamphetamine 

particularly are prone to produce the sensation 

of insects crawling on or burrowing in the 

skin (Siegel 1978, Elpern 1988). 

The 50 most commonly prescribed drugs in the 

United States list at least one symptom commonly 

attributed to delusory parasitosis (Table 4). These 

include erythema (56%), paresthesia (56%), pruritus 

(64%), urticaria (66%), and rash (92%). Although 

these side effects may be rare, the fact that 

these data are based on more than 2 billion prescriptions 

indicates that these drugs are being used 

extensively and that an increasing proportion of 

patients will experience these ancillary reactions and 

possibly attribute them to unseen "bugs" (Fig. 3). 

20 AMERICAN ENTOMOLOGIST • Spring 2000

Table 4. Fifty most commonly prescribed U.S. drugs and some side effects· 

Brand Name Generic Name Drug Type Erythema Paresthesia Pruritus Rash Urticaria 

Trimox, Augmenrin Amoxicillin antibiotic X X X X 

Prclllarin, Prempro Estrogens estrogen X X 

Synthroid, Levoxyl Levothyroxine thyroid X X 

Rancap, Lorcet Hydrocodone/APAP analgesic X X 

Prozac Fluoxetine antidepressant X X X X X 

Lanoxin Digoxin cardiovascular X 

Prilosec Omeprazole ulcer X X X X X 

Vasotec Enalapril hypertension X X X X X 

Zithromax Azirhromycin antibiotic X 

Norvasc Amlodipine angina X X X X X 

Zoloft Sertraline a ntidepressa nt X X X X X 

Claririn Loratadine antihistamine X X X X X 

Coullladin Warfarin thrombolytic X X X 

Zocor Simvastatin cardiovascular X X X X 

Furosemide, Lasix Furosemide hypertension X X X X X 

Paxil Paroxetine antidepressant X X X X X 

Albuterol, Ventolin Albuterol brochodilator X X X 

Zantac Ranitidine ulcer X X 

Zestril, Prinivil Lisinopril hypertension X X X X X 

Procardia, Adalat Nifedipine hypertension X X X X 

Cardizem Diltiazelll hypertension X X X X X 

Biaxin Claritbromycin antibiotic X X 

Ractrilll Trimeth/Sulfameth anribiotic X X X X 

Keflex Cephalexin antibiotic X X X X 

Tylenol with Codeine Aceta min op hen/Codeine analgesic X 

Glucophage Metformin diabetes X 

Cipro Ciprofloxacin antibiotic X X X X X 

[)arvocet, Darvon Propoxyphene N/APAP analgesic X 

Veetids Penicillin VK antibiotic X 

Pravachol Pravasrarin cardiovascular X X X X X 

Dyazide Triamterene/HCTZ cardiovascular X 

Ultral11 Tramadol analgesic X X X X 

Mocrin, Advil Ibuprofen analgesic X X X X X 

fl ytrin Terazosin cardiovascular X X X 

Alllbien Zolpidem sedative X X X 

Accupril Quinapril hypertension X X 

Relafen Nabul11etone analgesic X X X X X 

Elavil Amitriptyline antidepressant X X X 

Claritin Loratidine antihistamine X X X X X 

HUlllulin lnsulin-NPH diabetes X 

Dilalltin Phenytoin anticonvulsant X X 

Pepcid Famotidine ulcer X X X X 

Glucotrol Glipizide diabetes X X X X X 

Lotensin Benazepril hypertension X X X 

Cardura Doxazosin hypertension X X X 

Mevacor Lovastatin cardiovascular X X X X X 

Cefzil Cefprozil antibiotic X X X X 

Xanax Alprazolam sedative X X X 

Prednisone, Panasol Prednisone antiarthritic X X 

Tenorl11in, Atenolol Atenolol hypertension X X 

"Sandow ] 998, based on more than two billion 1997 U.S. prescriptions. 

Drugs disproportionately prescribed for the eld- fects: the elderly take multiple medications simultaerly 

such as those for heart conditions, glaucoma, neously (prescription and over-the-counter), freosteoporosis, 

impotence, and arthritis particularly quendy receive prescriptions from more than one 

may be predisposed to cause these side effects (May doctor, more frequently are confused by instrucand 

Terpenning 1991). These drugs include insu- tions or forget how often they have medicated themlin, 

estrogen, arthritis medications, hypertension selves, and drug pharmacokinetics vary by patient 

drugs, beta blockers, MAO inhibitors, and antide- age. Persons over 65 years old represent only 12% 

pressants. of the population but receive more than 30% of all 

Several factors contribute to the predisposition prescription drugs (Jones 1997). Older adults avof 

elderly people to experience adverse drug ef- erage three prescription medications per day, 15 

A.\tERICANENTOMOLOGIST• Volume 46, Number 1 21

" 

iImJ 

••....- 

\~- 

NOC o••n~1I)4.QQ 

100 PUlVUlES- No. 31 

PROZAe· 

R.UOXtTIE 

Fig. 3. Side effects of Prozac®, 

the fifth most commonly prescribed 

medication, include all five 

symptoms commonly attributed to 

delusory parasitosis-erythema, 

paresthesia, pruritus, rash, and 

urticaria. 

Table 5. Some web sites dealing with delusory parasitosis 

different prescriptions per year, and consume 70% 

of all over-the-counter drugs. Approximately 25% 

of their hospital admissions are a result of incorrect 

prescription drug usage. One in five Americans 

over the age of 60 regularly takes pain medication 

and one in four who does so experiences 

side effects caused by the medication; one in ten is 

hospitalized as a result (Chrischilles et al. 1992). 

Herbal remedies and nutritional supplements 

may produce untoward side effects including pruritus 

and urticaria (Huxtable 1990, Cetaruk and 

Aaron 1994). Additionally, they may interfere with 

or potentiate prescription and over-the-counter 

medications, resulting in unanticipated effects. 

Although this is by no means an exhaustive 

review of medication side effects, it does show that 

symptoms experienced by delusory parasitosis sufferers 

may have valid physiological causes, either 

in medical conditions or in the drugs prescribed 

for their treatment. Psychologists and dermatologists 

have noted that organic causes must be excluded 

before a diagnosis of psychogenic pruritus 

can be made (Freyne and Wrigley 1994, Gupta 

1995). 

Because of the numerous potential physiological 

causes of pruritus, urticaria, and paresthesia, it 

is understandable that physicians often do not attempt 

to treat underlying causes but, instead, prescribe 

palliatives or advise the patient to pursue 

entomological possibilities (which fits with the 

patient's inclinations, anyway). In these days of 

managed care, physicians have neither the time nor 

incentive to do a thorough medical workup or attempt 

to determine causation of obscure and nonlife-threatening 

symptoms. 

In teenagers and young adults, recreational drug 

use may be a more likely explanation for delusory 

parasitosis symptoms (Zanol et al. 1998). Drugs 

such as cocaine and methamphetamine particularly 

are noted for producing "formication," or the sensation 

of ants crawling in or on the skin (Ellinwood 

1969, Siegel 1978, Elpem 1988, Marschall et al. 

1991). Cocaine use is admitted by 19% of all 18- 

25 year olds and 26% of all 26-34 year olds; hallucinogens 

such as methamphetamines have been 

used by 12% of 18-25 year olds and 16% of 26- 

34 year olds (SAMHSA 1996). Ekbom's (1938) 

syndrome caused by drug use was featured in an 

episode of "The X Files" (Hinkle 1998), thus assuming 

its place in popular culture. 

Psychological Causes 

Scratching is a common primate displacement 

activity in response to tension, anxiety, and stress 

Cultural entomology http://www.insects.org/ced2/insects_psych.html 

Factsheet http://www.iane.unl.edu/ianrllanco/enviro/pest/facrsheets/009-95.htm 

Imaginary infestations http://www.medscape.com/SCPIIIM/1998/v15.n03/m4174.godd/ 

m4174.godd.html 

N arional Geographic http://www.nationalgeographic.com/media/ngm/9812Ifngm/ 

index.html 

(Schino et al. 1996). There are strong socio-psychological 

implications of self-grooming, reflecting 

group status, individual self-image, and psychological 

well-being. Touching, scratching, and rubbing 

are viewed as forms of self-assurance, consolation, 

and validation of the psyche (Schino et al. 

1991, Troisi et al. 1991). This dynamic is displayed 

in meetings, in one-on-one confrontations between 

individuals, and in other human interactions. 

Symptoms of anxiety, stress, tension, depression, 

and tiredness can manifest themselves as itching 

and tingling (Gieler and Knoll 1990, Gupta et 

al. 1994, Gupta 1995, Woodruff et al. 1997). Although 

it is generally recognized that stress can 

induce headaches, high blood pressure, acne, heart 

attacks, and ulcers, delusory parasitosis sufferers 

are reluctant to acknowledge that their derma tologic 

symptoms could be related to stress or depressIOn. 

Social isolation is one predisposing feature of 

delusory parasitosis. Some delusory parasitosis 

cases involve lonely people who need interactions 

with other humans (May and Terpenning 1991). 

Elderly people who live alone, seldom get out, seldom 

have visitors, or feel they have no purpose in 

life are prone to fixating on themselves and their 

health (Bernhard 1992, Freyne and Wrigley 1994). 

For many of these people, the illness itself is an 

important security factor (Laihinen 1991), allowing 

them to seek attention and evoke sympathy. 

Bell's Syndrome (the Power of Suggestion). Often, 

the fact that several people are experiencing 

the same sensation is used to demonstrate that it is 

not psychological. Scratching behavior is an atavistic 

primate response with high psychological 

contagiousness (de Leon et al. 1992). Thus, situations 

in which more than one person is complaining 

of the symptoms are not necessarily evidence 

that there is a common cause behind the symptoms. 

Entomologists who deal with delusory parasitosis 

cases will attest to this. Despite finding no 

arthropod in any samples provided, there is a 

strong urge to take a shower following these examinations. 

Consciously, one realizes that there is 

no infestation, but subconsciously one often feels 

the "creepy-crawlies" after looking through the 

victim's scurf. In fact, the author, while reading 

through the delusory parasitosis literature in preparing 

this article, found herself absentmindedly 

scratching; before the manuscript was completed, 

her arms and legs bore distinct scarification. 

Responses of the Entomologist or Pest 

Control Operator 

It always should be determined whether, in fact, 

an arthropod is involved (Table 5). Monitoring 

may include using cellophane tape to entrap the 

culprit while it is attacking the skin, glue boards to 

survey the environment, or a hand-operated 

vacuum 

cleaner to sample the area in which attacks 

are occurring (Potter 1992). Typical culprits include 

thrips brought in on flowers, bird or rodent 

mites from nests in the building, or cryptic pests 

22 AMERICAN ENTOMOLOGIST • Spring 2000

such as bed bugs or fleas (Webb 1993). If a causative 

agent is identified, the source can be eliminated 

and the problem solved. Otherwise, no pesticidal 

applications should be made (Potter 1992). 

Monitoring and careful investigation of the situation 

may indicate that, although no arthropod is 

involved, there are physical causes such as insulation 

being blown through air-handling systems or 

nylon fragments from newly installed carpet (Blum 

and Katz 1990, Potter 1992). Frequently, such 

modifications as improved sanitation, installation 

of antistatic devices, and increased humidity will 

reduce complaints. 

If no entomological cause can be identified, the 

individual should be referred to a physician and 

encouraged to pursue the possibility of one of the 

previously mentioned medical conditions serving 

as the basis of the symptomatology (Kushon et a!. 

1993). Meanwhile, the sufferer should be advised 

to discontinue using self-prescribed treatments. 

These materials, applied topically, are not good for 

the skin and may aggravate the problem. In particular, 

pesticidal shampoos and lotions should not 

be used more than stated specifically on the label; 

these are potent compounds that will increase skin 

sensitivity when overused. 

Responsible pest control firms have policies 

against treating for pests until a culprit has been 

identified. This is legally and ethically appropriate 

(St. Aubin 1981). Customers, however, frequently 

do not understand, expecting that the pest control 

operator will "just spray something." Pressure to 

comply may be extreme. By applying pesticides, the 

pest control operator is validating the customer's 

perception that there is a pest present. Unwarranted 

pesticidal applications increase the building's pesticide 

load. Pesticide exposure can increase symptom 

manifestations, both as psychological responses 

and as physiological reactions to the formulation. 

For instance, the alpha-cyano pyrethroids 

are known to produce cutaneous paresthesia 

(Pauluhn 1996), and some organophosphates 

produce dermatological manifestations following 

sustained exposure (Misra et a!. 1985). So, 

insecticide treatments made in delusory parasitosis 

cases may exacerbate the situation. 

Conclusion 

Although arthropod activity can cause irritation 

to humans, similar sensations can be produced 

by many other conditions. When there is no arthropod 

involvement, the condition is termed "delusory 

parasitosis" and is no longer within the 

scope of entomological expertise but appropriately 

devolves to health-care professionals. The 

entomologist's function is to determine whether 

insects or mites are involved and, if so, to identify 

and make recommendations for their suppression 

(Waldron 1972). Unfortunately, it typically is impossible 

to convince the individual that there are 

no "bugs" present, and recommendations to visit 

a health care professional virtually always are rebuffed 

(Lynch 1993). 

Entomologists should have the courage of their 

A.\tERICAN ENTOMOLOGIST • Volume 46, Number 1 

convictions. Once it has been determined that there 

are no arthropods involved in the case, this should 

be conveyed to the individual tactfully but firmly. 

The letter may be worded to make the point that, 

"Although examination of the specimens you provided 

yielded no evidence of arthropod involvement, 

the symptoms you are experiencing are real 

and deserve further investigation." The objective 

is to persuade the sufferer to go to a physician 

where, it is hoped, he or she may receive appropriate 

health care (Lynch 1993, Hinkle 1998). As 

Elliott (1944) observed over half a century ago, 

investigating delusory parasitosis is "an intriguing 

field for useful research, an opportunity for teamwork 

on the part of the pest control operator, the 

medical entomologist, the dermatologist, and the 

psychiatrist." ~ 

Acknowledgments 

I thank F. M. Oi, of the USDA-ARS, Center for 

Medical, Agricultural & Veterinary Entomology, 

Gainesville, Florida, who supplied the persistent encouragement 

that resulted in this article. Grateful 

appreciation goes to the more than 70 Cooperative 

Extension Specialists around the country who participated 

in our delusory parasitosis survey, as well 

as the other contributors who alerted me to valuable 

literature and sources. I am grateful to the on-line 

discussion group Entomo-I for providing diverse 

accounts of and perspectives on delusory parasitosis. 

Acknowledgment (without appreciation) goes 

to the hundreds of delusory parasitosis sufferers 

who have provided me this experience. 

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Nancy C. Hinkle, California's Extension 

Veterinary Entomologist, 

is based in the Department of 

Entomology at the University of 

California, Riverside. Her main 

research interests involve ectoparasites 

and arthropod pests of livestock, 

poultry, and companion 

animals; however, she becomes involved in DP investigations 

because sufferers frequently claim their "infestations" 

came from pets. Corresponding address: 

Department of Entomology, University of California, 

Riverside, CA 92521, NHinkle@citrus.ucr.edu. 

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