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The mistaken belief, or delusion, can be triggered by something as simple as an allergic reaction, a chemical sensitivity, emotional stress or even recreational drug use. As with other delusional disorders, professional psychological counseling is generally needed. See this UC Davis site for clinical definitions and treatment suggestions.

Entomologists are sometimes asked to investigate cases of mysterious bites that may or may not have physical manifestations such as skin lesions. These cases generally fall into two broad groups.

Most are some type of "mistaken identity" in which the person believes that some harmless insect or spider is biting/stinging them. Usually any associated skin irritation has an environmental explanation. In a small percentage are cases, however, the person has an unshakable belief that they are infested with an unseen "bug" and all attempts to find and identify the culprit have failed.

All such complaints should at least initially be investigated with the underlying assumption that a real arthropod infestation is present. There are a number of insects and mites that can cause real skin reactions and lesions (see Causes of Mysterious Bug Bites for a list of some real culprits). For example, bird/rodent/nest mites cause bites that can be very difficult to diagnose (see Bird Mite Bites). The following signs, however, are indicative of imagined infestations in my experience:

Signs of DOP (this is my own list and is probably not exhaustive)

• reports bites or skin lesions from unknown causes
• reports they alone are being bitten or, interestingly, close family members also "infested"
• reports that home or workplace "infested", in addition to a "personal infestation"
• reports resorting to self-treatment with insecticides or other harsh chemicals (bleach, kerosene)
• reports fear for others "becoming infested" which leads to self-imposed isolation
• reports multiple, unsatisfactory contacts with the medical or pest control community
• reports that home has been abandoned because of the "infestation"
• reports that "bugs" are invisible or disappear after capture
• submits elaborately wrapped samples, often with very detailed collection information
• submits samples of body tissue or swabs

[Delusions of Parasitosis (pdf)] - This file contains references to DOP from the scientific literature compiled in 1997.

[Mites That Bite Guide (pdf)] - There are a number of very small mites that actually bite and cause skin lesions. These causes must be excluded before a diagnosis of delusions can be made.

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