Illusory and Delusory Parasitosis

BY BARB OGG, PHD,

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.

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 is an arthropod named the “house dust mite,” but these very small mites do not bite people, but feed on sloughed skin cells, dander and other organic debris.

When dust mites die, their bodies disintegrate into very small particles. Persons who have allergic sensitivities may experience an allergic reaction to the fine particles; the most typical reaction is asthma rather than skin irritations.

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. Occasionally, people claim that they are being bitten by microscopic bugs. These claims prove to be mites carried by pet cats or pesty rodents or birds (usually pigeons or barn swallows) that live on or near the homes of these unfortunate people. Because humans are not the usual host animal, the problem is controlled by removing the rodent or bird infestation or having the cats treated by a veterinarian.

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 often a problem with older sedentary persons. Nursing homes sometimes may have to deal with infestations of scabies mites. Scabies mite infestations must be identified and treated by a dermatologist who prescribes medicated ointment and lotion.

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. Physical factors may include dry air; static electricity; household or personal products like disinfectants, detergents, cosmetics, or jewelry. Environmental pollutants also may cause skin irritation. These pollutants include microscopic fibers like fiberglass or paper splinters.

In addition, indoor air pollution can cause “sick or tight-building syndrome.” Physiological factors include sensitivity (i.e., allergies) to any of the above physical factors. One should be aware that skin sensitivities and allergies may change as we get older and our skin changes. There also may be diseases and disorders such as diabetes or neurological disorders such as shingles that may result in skin problems. 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. 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.

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. 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.