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Invisible Itches: Insect and Non-Insect Causes

Mystery Bugs

Pinprick-like biting sensations, usually on exposed skin and often producing inflammations that resemble insect bites, can be a persistent problem in some buildings. Occupants tend to blame these "bites" on some sort of pest infestation, typically fleas (which are rare in schools or office buildings), or "paper mites" (which do not exist). Demands for spraying of the affected space are often carried out in the absence of any evidence that biting insects are present. In fact, "paper mites" are almost always tiny, irritating particles like paper shards that constitute a cleaning or indoor air pollution problem rather than a pest problem.

The Role of Management

The most common mistake of management in "paper mite" situations is to automatically request a pesticide treatment, thereby incurring liability in the event occupants experience adverse reactions to the chemical. The second most common mistake is for supervisors to dismiss the complaints of biting as imagination. Although there are cases where people imagine they are being attacked by unseen parasites, most instances of biting-like sensations in buildings involve a genuine source of skin irritation. The circumstances can be further complicated, because health care professionals unfamiliar with the "paper mite syndrome" frequently misdiagnose the resulting welts as insect bites. Other people may believe that microscopic dust mites are involved; dust mites are real, but they cause breathing distress rather than bites. Finally, it is normal for the coworkers of a person complaining about "paper mites" to develop a heightened sensitivity to their own skin irritations (many caused away from the workplace) through the "power of suggestion.

M. F. Potter and P. G. Koehler

Once in a while, nearly everyone experiences the irritation of an unexpected itch or the sensation of something crawling over the skin. Other times, the irritation may feel more like an insect bite. These reactions can become so annoying for some people that they are forced to seek professional help. Even though actual pests may not have been observed, the irritation is often attributed to "bugs," and an insecticide is applied in the hope that the problem will be resolved. Unfortunately, pesticides seldom work in these situations, and they may even cause irritation and additional health problems.

It is important to recognize that there are many potential causes of itching and irritation other than pests. Allergies, cosmetics, medications, and environmental contaminants all can produce reactions similar to insect bites. While this makes the experience no less real or unpleasant for the affected individual, it underscores the importance of keeping an open mind to the possibility of non-insect causes of such reactions. Much like a detective, one should attempt to rule out all potential sources of irritation through the process of elimination. this publication will help you to determine if the irritation a person is experiencing is due to pests or to other (non-insect) causes.

Sources of Irritation

Itches and real or perceived bites of unknown origin can usually be attributed to one of four general sources:

Household Products

There are literally hundreds of non-insect agents capable of causing itching and irritation. Household products are involved far more often than are pests and may cause skin reactions similar to insect bites. Products most often implicated include phosphate detergents, soaps, cosmetics, ammonia-based cleaning agents, hair products, medications, printing inks (especially from multi-form carbonless carbon paper), and certain types of clothing, particularly those which contain fire retardants. If a connection can be made between irritation and exposure to one of these potential irritants, avoiding further exposure may correct the problem. A dermatologist can usually confirm that a product, rather than a pest, is causing the irritation.

Environmental Factors

When two or more individuals experience irritation in the absence of pests, the cause is likely to be environmental conditions or contaminants dispersed in the air. The irritant's) may be either physical or chemical in nature.

Physical Irritants

The most common physical irritants are tiny fragments of paper, fabric, or insulation. When these fibers contact the skin, they can produce symptoms ranging from a "crawling sensation" to intense itching accompanied by a rash, welts, or open sores. If fibers or fragments are involved, the irritation usually occurs over exposed areas of the body such as arms, legs, neck, and head.

Irritation produced by paper fragments is especially common in offices where large quantities of paper are processed daily. Continuous-feed paper from computers and multi-page forms generate large amounts of fragments, resulting in accumulations on desktops and other surfaces. Newly installed or badly worn synthetic carpet, drapes or upholstery also shed fibers which can irritate skin.

Other potential sources of irritation are insulation fibers released into the air by heating/cooling systems in need of repair and sound-deadening fibers embedded into drop-ceiling tiles. These latter sources are especially suspect if there have been problems with the air-handling system or recent repair work on the ceiling.

Irritation is aggravated by static electricity which increases the attraction of the tiny charged fibers to exposed skin. Low humidity, electronic equipment, and nylon (e.g., from carpeting, upholstery, or women's stockings) all increase levels of static electricity and the potential for problems from fragments or fibers. Static electricity may also cause body hair to move, giving the impression of insects crawling over the skin.

If fibers or fragments are suspected of causing the reactions, floors, rugs, work surfaces, and furniture should be thoroughly and routinely vacuumed, and desktops and tables wiped down with a damp cloth. Static-reducing measures should also be considered such as raising the humidity level of the air and installing static-resistant mats and pads under chairs and electronic equipment in offices. Anti-static sprays can be used to treat seat cushions and nylon stockings.

Dry air alone can cause irritation, producing a condition known as "winter itch." As skin loses moisture, itching results. A similar reaction can occur from changes in temperature; these tend to make skin more sensitive. A skin moisturizer is often helpful in these situations.

Airborne Chemical Irritants

Indoor air pollution can be a serious problem in modern office buildings and other energy-efficient structures where air is recirculated over and over. Indoor air pollution can also be a problem in homes. As the concentration of chemical contaminants in the air increases, people may experience dizziness, headaches, and eye, nose, or throat irritation. Certain air-borne contaminants can also produce rashes and skin irritation similar to insect bites. Chemical contaminants most often responsible for these reactions include ammonia-based cleaning agents, formaldehyde emitted from wall and floor coverings, tobacco smoke, and solvents and resins contained in paints, glues, adhesives, and pesticides repeatedly applied for control of suspected pest infestations.

Reactions to airborne chemicals most often occur in buildings with inadequate ventilation, especially those that are new or have been refurbished with new paint or wall or floor coverings. If indoor air pollutants rather than insects are suspected, you may wish to consult an industrial hygienist who is equipped to monitor ventilation levels and the presence of allergy-producing contaminants. Companies specializing in environmental health monitoring have listings in the telephone directories of most metropolitan areas.

Health-Related Conditions

Health-related conditions may be responsible for irritation mistakenly attributed to insects. Itching and skin irritation are common during pregnancy (especially during the last trimester) and may also occur in conjunction with diabetes, liver, kidney, and thyroid disease, and shingles. Food allergies are another common cause of itching and irritation.

A person's emotional state can also induce skin reactions that can be mistaken for insect bites. Stress and conflict at work or home can produce itching and irritation. The itching response can be induced in other individuals simply by the "power of suggestion;" i.e., when one person in a group feels an itch or bite and begins to talk about it, others also feel the urge to scratch as well (a condition known as Bell's syndrome).

Delusory parasitosis is a more serious emotional disorder characterized by an irrational fear that living organisms are infesting a person's body. Cases of delusory parasitosis often have similar symptoms and patterns of behavior. Patients typically report "bugs" invading their ears, nose, eyes, and other areas of their body. The "creatures" frequently disappear and reappear and change colors while being observed. Specimens brought in for identification usually consist of bits of dead skin, hair, lint, and miscellaneous debris. The skin of the individual is often severely irritated from desperate scratching, excessive bathing, and application of ointments, bleaches, gasoline and other solvents. While these occurrences may seem bizarre to persons who are not affected, they are frighteningly real to the patient. Delusory parasitosis as well as other suspected emotional or medical conditions should be brought to the attention of a dermatologist or other physician.

Finding A Solution

There is no easy way to pinpoint the cause of so-called "invisible" itches. The most important consideration in determining if pests are involved is whether anyone has actually seen or captured any "bugs" as the itching or irritation is occurring. Most insects and mites which bite humans can be seen without magnification if you look carefully. Pesticides should not be applied unless there is actual evidence that pests are the cause of irritation.

In most cases, pests will not be involved and relief from irritation will be outside the realm of pest control. Approaching these problems in a rational and methodical manner will increase the chances of finding the sources of irritation. Refer to the list of likely irritants in Table 1 and follow suggestions mentioned in this publication for alleviating the condition. If the problem persists, you may need to employ the services of a pest control professional, dermatologist, and/or environmental consultant.

Household Products

detergents (especially phosphate-based)


cosmetics/hair products

ammonia-based cleansers


printing inks (e.g., carbonless)

clothing (especially fire retardant)



Environmental Factors

A. Physical irritants

paper, fabric, or insulation fibers

low humidity

seasonal changes in temperature

static electricity

B. Chemical irritants

formaldehyde (e.g., from particle board, wall and floor coverings)


solvents/resins associated with paints and adhesives

tobacco smoke

volatiles from asphalt and tar installation



Health-Related Conditions


communicable diseases (e.g., chicken pox, measles)


diabetes, liver, or kidney disorders

food allergies

insect phobias



* Many of these pests are large enough to be seen without magnification. One should also consider the possibility of delayed irritation such as from bites obtained while outdoors.




1. This document is ENY-269, one of a series of the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: March 1995. Revised: February 2000. Please visit the EDIS Website at Additional information on these organisms, including many color photographs, is available at the Entomology and Nematology Department WWW site located at

2. M. F. Potter, The University of Kentucky, and P. G. Koehler, professor, Entomology and Nematology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity - Affirmative Action Employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For information on obtaining other extension publications, contact your county Cooperative Extension Service office.

Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Larry R. Arrington, Interim Dean

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