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Clinical Summary

Delusional infestation (delusional parasitosis) is a rare disorder in which individuals have the delusion that they are infected by a living organism such as worms, mites, bugs, and parasites. Rational reasoning does not impact the delusion. Delusional infestation is more common in patients over the age of 50 and in women. Three of four patients have a concurrent mental health illness, including depression, anxiety, and drug abuse. Such patients often present with excoriations (Fig. 27.31) and frequently complain of pruritis. It is common for patients suffering from this disorder to present with specimens to support their argument such as bags of stool (Fig. 27.32) or specimens including string or scabs that they have picked from their skin.

FIGURE 27.31

Delusional Infestation—Multiple Excoriations. Numerous excoriations within reach of the patient’s hands combined with a belief that the parasites are buried within the skin are characteristic of a delusional infestation disorder. Note the gloves this patient is wearing to prevent the spread of the parasites. (Photo contributor: Lawrence B. Stack, MD.)

FIGURE 27.32

Delusional Infestation—Bags of Stool. Patients with delusional infestation will often collect the “parasites” in bags of stool or urine as evidence of their affliction. (Photo contributor: Lawrence B. Stack, MD.)

Management and Disposition

A nonconfrontational approach to the patient with delusional infestation is recommended, and reassurance can often be helpful in obtaining patient buy-in to a multimodal approach involving further evaluation for the suspected infestation in addition to psychiatric referral as antipsychotics have demonstrated benefit for such patients.


  1. Management of delusional infestation often requires a nonconfrontational approach requiring the avoidance of dismissing the patient’s concerns as well as not explicitly supporting such beliefs.

  2. Antipsychotics are the mainstay of treatment for delusional infestation, although persuading patients to agree to pharmacotherapy is difficult.

  3. Do not give the patient with a delusional infestation a chance to refuse seeing a psychiatrist. Simply ask the psychiatrist to see them.

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