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Illusory & Delusory Parasitosis

scratching an arm

I almost hate to do this because after reading this some of you will be scratching yourselves, but in the winter it's a little harder to come up with some bug information. I want to touch on an interesting but fortunately rare occurrence, illusory and delusory parasitosis. This sounds a lot worse than it is, but for a very small part of the population it is a real problem. Essentially, there are instances where people believe that they are being bitten by insects when they are not. A lot of this information comes from Barb Ogg's Lancaster Co. "Insects, Spiders, Mice and More" Web page.

Some people encounter "bites," itching, or skin irritations thought to be caused by insects but for which no insects can be identified. Illusory parasitosis is one name used to describe bite-like symptoms caused by non-animal environmental factors. There is a long list of potential causes for "biting" sensations or skin irritation not caused by insects. The cause may be physical, physiological, psychological or combinations of these factors. A common cause could be an allergic reaction to almost anything. Names that people have invented for the nonexistent arthropods assumed to be the cause of the bites are "paper mites," "sand fleas," and "cable mites." There are no such insects.

There are only a few biting insects that produce skin reactions, and these are large enough to be seen and readily identified. Biting pests most commonly encountered include fleas, head lice, ticks, bat bugs, bed bugs, and mosquitoes. Body lice are relatively uncommon in the U.S. The only mites that infest humans are called scabies mites which cause dermatitis. Dermatitis from scabies mites is almost exclusively found on the hands, wrists, feet, ankles, and elbows and is most likely a problem with older sedentary persons. Nursing homes sometimes may have to deal with infestations of scabies mites. Scabies mites are identified and treated by a dermatologist who prescribes medicated ointment and lotion.

Some individuals may experience a heightened psychological state related to stress in their lives from increased anxiety, anger, and nervousness. Occasionally these persons may believe skin irritations are caused by insect bites, but the biting insects cannot be found. If environmental factors are not the cause of the dermatitis, the person may be suffering from delusory parasitosis. Delusory parasitosis is "an erroneous, unshakable belief that the skin is infested with some parasite." When asked to describe the so-called parasite (i.e., insect), persons suffering from this malady often give similar descriptions of these "imaginary" parasites. They are usually "microscopic"; they often "change color" so they cannot be seen or caught easily. Sometimes they "disappear" when a person tries to catch them. Some persons may think the imaginary insect "lives in their skin pores"; others may see "maggots coming out of their skin." Persons suffering from delusory parasitosis have a serious psychological disorder and might benefit greatly from counseling with a capable psychotherapist. These individuals may seem to be normal in other respects.

In my own experience I have only encountered two individuals who I believe had these condition(s). One was an elderly woman who brought in samples in a water bottle or an envelope with "insects and insect parts" for once a week for about 4-6 weeks. The only thing we ever found using our microscope was lint and dirt particles. She would also show us her "bites". Of course, she was scratching herself so hard that she actually did cause herself skin irritations. After some discussion we found that her doctor had sent her to us, he had given up trying to treat her problem. I believe she finally came to a realization after talking about it and showing her the samples she had brought in. Again, this was an intelligent, well-spoken individual.

The other individual was a man who would put scotch tape on his head to trap the "bugs" then remove it and bring in the tape for us to view. We never found any. In this instance we think his symptoms may have been a reaction to fiberglass insulation where he worked. He also was scratching himself and adding to the effect. The most interesting thing about this case is that his doctor prescribed a bottle of heavily diluted insecticide that he could rub on his skin to treat himself. The insecticide was malathion, once commonly used for many insect problems but not much anymore. The bottle cost about $100 and there was about 50 cents worth of insecticide in it. He did not come back, possibly by applying the insecticide a placebo effect occurred and he considered himself free of the "bugs". Repeated application of pesticides or disinfectants to the premises or body does not cure illusory or delusory parasitosis but may be a cause of further skin irritation and allergies.

Obviously, entomologists are not the appropriate specialists for diagnosis of causes of dermatitis other than those caused by insects. Persons suffering from skin irritation of unknown cause should work closely with their general physician, a dermatologist or allergist. If there is a history of psychological stress, consultation with a psychologist or psychiatrist may be helpful.

Image of Keith Jarvi
Keith Jarvi
Extension Educator - Crops & Integrated Pest Management
Keith Jarvi has been with the University of Nebraska since 1979. He received a Master’s Degree in Entomology from North Dakota State University and a Bachelor of Arts degree in Biology from Gustavus Adolphus College in St. Peter, MN. His area of focus is Crops and Integrated Pest Management. As far as insect id he has seen a lot of interesting specimens, but there are always a few surprises every year.

Contact Keith at:
Dixon County Extension
57905 866 Rd
Concord NE 68728-2828
(402) 584-3819