Vector-Borne and Zoonotic Diseases Program

Delusory Parasitosis

Health officials and entomologists sporadically receive requests from the public to identify ecto-(external) parasites.  The most commonly encountered ectoparasites are blood feeding arthropods such as head and pubic lice, fleas, ticks and scabies mites.  Persons suspected of having scabies are referred to their physician for treatment.  Most ectoparasite problems can be readily identified/diagnosed, and recommendations for their control can be made.

Occasionally, people complaining of ectoparasite infestations are seen where evidence of true infestation is lacking.  Repeated examinations by doctors and specimen identifications by health officials and/or entomologists fail to turn-up true parasites.  These  "parasitized" people are often very insistent that they see and feel "bugs" emerging from their pores, flowing through their veins, and/or emerging from their mouth and rectum.  They may also see these "parasites" crawling, jumping or flying throughout their homes and automobiles, and yet no one else can see them.  Repeated attempts to treat themselves and control bugs in their homes are unsuccessful.

These people suffer from a psychological condition called "delusory parasitosis" which is described as an unshakable belief that live organisms (or other foreign materials) are infesting the body.  Consultations with delusory parasitosis (DP) case patients are relatively common. Different DP cases often describe similar symptoms and problems, many of which are unrealistic from a biological standpoint:

  • These patients typically complain of sensations of biting (by bugs), itching, crawling or burning.
  • The infesting "bugs" are black or white at first, but may change color later. The "bugs" may also change their shape and appearance. For example, the parasites may change into inanimate objects.
  • The "bugs" are capable of moving rapidly such as jumping long distances.
  • The "bugs" often infest clothing and/or linen or may come out of common household items such as cosmetics and toothpaste.
  • The "bug" infestations may be so severe as to force the person to move away from his/her home.  In most cases, the "parasite problem" reappears in the new home.
  • Family members will often support the contention of an infestation even though they are not afflicted and cannot see the insects

The delusionary parasite problems can seem very real and be very distressing to DP patients, and they have been known to take drastic measures to control the problem.  DP patients will sometimes inflict wounds and create sores in the process of scratching or digging "bugs" out of their skin.  Many will apply caustic substances to their skin such as strong soaps, detergents, kerosene, insect repellents and even household pesticides.  The skin irritation that often develops from the constant exposure to various chemicals tends to reinforce the parasite delusions.

In dealing with suspect cases of delusory parasitosis, it is very important to examine bug specimens and other evidence to rule out the possibility of true infestation.  In some cases, the delusionary bug problems are triggered by a previous lice or scabies infestation, and even though the actual infestation had been treated successfully, the delusions persist.  DP patients often mail-in or bring-in specimens collected on scotch tape, wrapped in paper, or placed in jars.  Material that is identified by the patient as the offending parasites usually consist of lint, dead skin, scabs, dirt or plant fragments. True arthropods are rarely observed in samples, but when they are, they are not of a parasitic nature.

After ruling out the possibility of true parasites, the entomologist or health official explains to the DP patient that there is no evidence of parasites. DP patients are urged to cease using harsh remedies and chemicals, removing a major source of irritation. This approach is successful in some cases of DP.

A real dilemma exists in cases where the delusions persist.  Most DP patients are unwilling to seek psychiatric care since they are convinced that their problem is not delusional. Since the problem is of a psychological nature and not entomological, there is little else that an entomologist or health official can do.

This information is based on VBZD Section consultations with DP cases, and from:  Waldron, W. G. (1962). The Role of the Entomologist in Delusory Parasitosis (Entomophbia). Bull. Ent. Soc. Amer. 8:81-83.